From 468c49f91bc3c2d0680d56b99042b18f81c9e829 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Mon, 29 Apr 2024 14:48:56 -0700
Subject: [PATCH 1/5] Improve static analysis in Performance Lab plugin files

---
 includes/admin/load.php                       |  30 +++---
 includes/admin/plugins.php                    |   4 +-
 includes/admin/server-timing.php              |  12 ++-
 .../class-perflab-server-timing-metric.php    |  14 +--
 .../class-perflab-server-timing.php           |  26 ++---
 includes/server-timing/defaults.php           |   6 +-
 includes/server-timing/load.php               |  63 ++++++-----
 includes/server-timing/object-cache.copy.php  |   2 +-
 .../audit-autoloaded-options/helper.php       |  20 ++--
 .../audit-autoloaded-options/hooks.php        |  14 +--
 .../audit-enqueued-assets/helper.php          |  24 +++--
 .../audit-enqueued-assets/hooks.php           |  14 +--
 includes/site-health/avif-support/helper.php  |   4 +-
 includes/site-health/avif-support/hooks.php   |   6 +-
 includes/site-health/webp-support/helper.php  |   4 +-
 includes/site-health/webp-support/hooks.php   |   6 +-
 load.php                                      |  16 +--
 tests/includes/server-timing/load-tests.php   | 100 +++++++++++++-----
 .../audit-enqueued-assets-test.php            |   4 +-
 19 files changed, 219 insertions(+), 150 deletions(-)

diff --git a/includes/admin/load.php b/includes/admin/load.php
index 5d48d9c8b8..0a3e04d218 100644
--- a/includes/admin/load.php
+++ b/includes/admin/load.php
@@ -14,6 +14,8 @@
  *
  * @since 1.0.0
  * @since 3.0.0 Renamed to perflab_add_features_page().
+ *
+ * @return string|false Hook suffix.
  */
 function perflab_add_features_page() {
 	$hook_suffix = add_options_page(
@@ -32,6 +34,8 @@ function perflab_add_features_page() {
 
 	return $hook_suffix;
 }
+
+// @phpstan-ignore-next-line
 add_action( 'admin_menu', 'perflab_add_features_page' );
 
 /**
@@ -41,7 +45,7 @@ function perflab_add_features_page() {
  * @since 3.0.0 Renamed to perflab_load_features_page(), and the
  *              $module and $hook_suffix parameters were removed.
  */
-function perflab_load_features_page() {
+function perflab_load_features_page(): void {
 	// Handle script enqueuing for settings page.
 	add_action( 'admin_enqueue_scripts', 'perflab_enqueue_features_page_scripts' );
 
@@ -58,7 +62,7 @@ function perflab_load_features_page() {
  * @since 1.0.0
  * @since 3.0.0 Renamed to perflab_render_settings_page().
  */
-function perflab_render_settings_page() {
+function perflab_render_settings_page(): void {
 	?>
 	<div class="wrap">
 		<?php perflab_render_plugins_ui(); ?>
@@ -76,7 +80,7 @@ function perflab_render_settings_page() {
  *
  * @param string $hook_suffix The current admin page.
  */
-function perflab_admin_pointer( $hook_suffix ) {
+function perflab_admin_pointer( string $hook_suffix ): void {
 	// Do not show admin pointer in multisite Network admin or User admin UI.
 	if ( is_network_admin() || is_user_admin() ) {
 		return;
@@ -114,11 +118,11 @@ function perflab_admin_pointer( $hook_suffix ) {
  * @since 1.0.0
  * @since 2.4.0 Optional arguments were added to make the function reusable for different pointers.
  *
- * @param string $pointer_id Optional. ID of the pointer. Default 'perflab-admin-pointer'.
- * @param array  $args       Optional. Pointer arguments. Supports 'heading' and 'content' entries.
- *                           Defaults are the heading and content for the 'perflab-admin-pointer'.
+ * @param string                                    $pointer_id Optional. ID of the pointer. Default 'perflab-admin-pointer'.
+ * @param array{heading?: string, content?: string} $args       Optional. Pointer arguments. Supports 'heading' and 'content' entries.
+ *                                                              Defaults are the heading and content for the 'perflab-admin-pointer'.
  */
-function perflab_render_pointer( $pointer_id = 'perflab-admin-pointer', $args = array() ) {
+function perflab_render_pointer( string $pointer_id = 'perflab-admin-pointer', array $args = array() ): void {
 	if ( ! isset( $args['heading'] ) ) {
 		$args['heading'] = __( 'Performance Lab', 'performance-lab' );
 	}
@@ -204,7 +208,7 @@ function perflab_plugin_action_links_add_settings( $links ) {
  *
  * @since 2.3.0
  */
-function perflab_dismiss_wp_pointer_wrapper() {
+function perflab_dismiss_wp_pointer_wrapper(): void {
 	if ( isset( $_POST['pointer'] ) && 'perflab-admin-pointer' !== $_POST['pointer'] ) {
 		// Another plugin's pointer, do nothing.
 		return;
@@ -219,7 +223,7 @@ function perflab_dismiss_wp_pointer_wrapper() {
  * @since 2.8.0
  * @since 3.0.0 Renamed to perflab_enqueue_features_page_scripts().
  */
-function perflab_enqueue_features_page_scripts() {
+function perflab_enqueue_features_page_scripts(): void {
 	// These assets are needed for the "Learn more" popover.
 	wp_enqueue_script( 'thickbox' );
 	wp_enqueue_style( 'thickbox' );
@@ -231,7 +235,7 @@ function perflab_enqueue_features_page_scripts() {
  *
  * @since 3.0.0
  */
-function perflab_install_activate_plugin_callback() {
+function perflab_install_activate_plugin_callback(): void {
 	check_admin_referer( 'perflab_install_activate_plugin' );
 
 	require_once ABSPATH . 'wp-admin/includes/plugin.php';
@@ -273,9 +277,9 @@ function perflab_install_activate_plugin_callback() {
  *
  * @since 3.0.0
  */
-function perflab_print_features_page_style() {
+function perflab_print_features_page_style(): void {
 	?>
-<style type="text/css">
+<style>
 	.plugin-card .name,
 	.plugin-card .desc, /* For WP <6.5 versions */
 	.plugin-card .desc > p {
@@ -297,7 +301,7 @@ function perflab_print_features_page_style() {
  *
  * @since 2.8.0
  */
-function perflab_plugin_admin_notices() {
+function perflab_plugin_admin_notices(): void {
 	if ( ! current_user_can( 'install_plugins' ) ) {
 		$are_all_plugins_installed = true;
 		$installed_plugin_slugs    = array_map(
diff --git a/includes/admin/plugins.php b/includes/admin/plugins.php
index 923cf8bde0..dbc3f9a096 100644
--- a/includes/admin/plugins.php
+++ b/includes/admin/plugins.php
@@ -81,7 +81,7 @@ function perflab_get_standalone_plugins(): array {
  *
  * @since 2.8.0
  */
-function perflab_render_plugins_ui() {
+function perflab_render_plugins_ui(): void {
 	require_once ABSPATH . 'wp-admin/includes/plugin-install.php';
 	require_once ABSPATH . 'wp-admin/includes/plugin.php';
 
@@ -283,7 +283,7 @@ function perflab_install_and_activate_plugin( string $plugin_slug ): ?WP_Error {
  *
  * @param array{name: string, slug: string, short_description: string, requires_php: string|false, requires: string|false, requires_plugins: string[], version: string, experimental: bool} $plugin_data Plugin data augmenting data from the WordPress.org API.
  */
-function perflab_render_plugin_card( array $plugin_data ) {
+function perflab_render_plugin_card( array $plugin_data ): void {
 
 	$name        = wp_strip_all_tags( $plugin_data['name'] );
 	$description = wp_strip_all_tags( $plugin_data['short_description'] );
diff --git a/includes/admin/server-timing.php b/includes/admin/server-timing.php
index 94a520ec2f..3db996e929 100644
--- a/includes/admin/server-timing.php
+++ b/includes/admin/server-timing.php
@@ -18,6 +18,8 @@
  * Adds the Server-Timing page to the Tools menu.
  *
  * @since 2.6.0
+ *
+ * @return string|false Hook suffix.
  */
 function perflab_add_server_timing_page() {
 	$hook_suffix = add_management_page(
@@ -35,6 +37,8 @@ function perflab_add_server_timing_page() {
 
 	return $hook_suffix;
 }
+
+// @phpstan-ignore-next-line
 add_action( 'admin_menu', 'perflab_add_server_timing_page' );
 
 /**
@@ -42,7 +46,7 @@ function perflab_add_server_timing_page() {
  *
  * @since 2.6.0
  */
-function perflab_load_server_timing_page() {
+function perflab_load_server_timing_page(): void {
 	/*
 	 * This settings section technically includes a field, however it is directly rendered as part of the section
 	 * callback due to requiring custom markup.
@@ -149,7 +153,7 @@ static function () {
  *
  * @since 2.6.0
  */
-function perflab_render_server_timing_page() {
+function perflab_render_server_timing_page(): void {
 	?>
 	<div class="wrap">
 		<?php settings_errors(); ?>
@@ -173,7 +177,7 @@ function perflab_render_server_timing_page() {
  *
  * @param string $slug Slug of the field and sub-key in the Server-Timing option.
  */
-function perflab_render_server_timing_page_hooks_field( $slug ) {
+function perflab_render_server_timing_page_hooks_field( string $slug ): void {
 	$options = (array) get_option( PERFLAB_SERVER_TIMING_SETTING, array() );
 
 	// Value for the sub-key is an array of hook names.
@@ -205,7 +209,7 @@ class="large-text code"
  *
  * @since 2.6.0
  */
-function perflab_render_server_timing_page_output_buffering_section() {
+function perflab_render_server_timing_page_output_buffering_section(): void {
 	$slug           = 'output_buffering';
 	$field_id       = "server_timing_{$slug}";
 	$field_name     = PERFLAB_SERVER_TIMING_SETTING . '[' . $slug . ']';
diff --git a/includes/server-timing/class-perflab-server-timing-metric.php b/includes/server-timing/class-perflab-server-timing-metric.php
index 7b16476078..d7ac259432 100644
--- a/includes/server-timing/class-perflab-server-timing-metric.php
+++ b/includes/server-timing/class-perflab-server-timing-metric.php
@@ -44,7 +44,7 @@ class Perflab_Server_Timing_Metric {
 	 *
 	 * @param string $slug The metric slug.
 	 */
-	public function __construct( $slug ) {
+	public function __construct( string $slug ) {
 		$this->slug = $slug;
 	}
 
@@ -55,7 +55,7 @@ public function __construct( $slug ) {
 	 *
 	 * @return string The metric slug.
 	 */
-	public function get_slug() {
+	public function get_slug(): string {
 		return $this->slug;
 	}
 
@@ -67,9 +67,9 @@ public function get_slug() {
 	 *
 	 * @since 1.8.0
 	 *
-	 * @param int|float $value The metric value to set, in milliseconds.
+	 * @param int|float|mixed $value The metric value to set, in milliseconds.
 	 */
-	public function set_value( $value ) {
+	public function set_value( $value ): void {
 		if ( ! is_numeric( $value ) ) {
 			_doing_it_wrong(
 				__METHOD__,
@@ -110,14 +110,14 @@ public function get_value() {
 	}
 
 	/**
-	 * Captures the current time, as a reference point to calculate the duration of a task afterwards.
+	 * Captures the current time, as a reference point to calculate the duration of a task afterward.
 	 *
 	 * This should be used in combination with {@see Perflab_Server_Timing_Metric::measure_after()}. Alternatively,
 	 * {@see Perflab_Server_Timing_Metric::set_value()} can be used to set a calculated value manually.
 	 *
 	 * @since 1.8.0
 	 */
-	public function measure_before() {
+	public function measure_before(): void {
 		$this->before_value = microtime( true );
 	}
 
@@ -129,7 +129,7 @@ public function measure_before() {
 	 *
 	 * @since 1.8.0
 	 */
-	public function measure_after() {
+	public function measure_after(): void {
 		if ( ! $this->before_value ) {
 			_doing_it_wrong(
 				__METHOD__,
diff --git a/includes/server-timing/class-perflab-server-timing.php b/includes/server-timing/class-perflab-server-timing.php
index bf9fae647e..8208c780b2 100644
--- a/includes/server-timing/class-perflab-server-timing.php
+++ b/includes/server-timing/class-perflab-server-timing.php
@@ -17,7 +17,7 @@ class Perflab_Server_Timing {
 	 * Map of registered metric slugs and their metric instances.
 	 *
 	 * @since 1.8.0
-	 * @var array
+	 * @var array<string, Perflab_Server_Timing_Metric>
 	 */
 	private $registered_metrics = array();
 
@@ -25,7 +25,7 @@ class Perflab_Server_Timing {
 	 * Map of registered metric slugs and their registered data.
 	 *
 	 * @since 1.8.0
-	 * @var array
+	 * @var array<string, array{measure_callback: callable, access_cap: string}>
 	 */
 	private $registered_metrics_data = array();
 
@@ -36,8 +36,8 @@ class Perflab_Server_Timing {
 	 *
 	 * @since 1.8.0
 	 *
-	 * @param string $metric_slug The metric slug.
-	 * @param array  $args        {
+	 * @param string                                                $metric_slug The metric slug.
+	 * @param array{measure_callback: callable, access_cap: string} $args        {
 	 *     Arguments for the metric.
 	 *
 	 *     @type callable $measure_callback The callback that initiates calculating the metric value. It will receive
@@ -48,7 +48,7 @@ class Perflab_Server_Timing {
 	 *                                      needs to be set to "exist".
 	 * }
 	 */
-	public function register_metric( $metric_slug, array $args ) {
+	public function register_metric( string $metric_slug, array $args ): void {
 		if ( isset( $this->registered_metrics[ $metric_slug ] ) ) {
 			_doing_it_wrong(
 				__METHOD__,
@@ -98,7 +98,7 @@ public function register_metric( $metric_slug, array $args ) {
 		$this->registered_metrics[ $metric_slug ]      = new Perflab_Server_Timing_Metric( $metric_slug );
 		$this->registered_metrics_data[ $metric_slug ] = $args;
 
-		// If the current user has already been determined and they lack the necessary access,
+		// If the current user has already been determined, and they lack the necessary access,
 		// do not even attempt to calculate the metric.
 		if ( did_action( 'set_current_user' ) && ! current_user_can( $args['access_cap'] ) ) {
 			return;
@@ -116,7 +116,7 @@ public function register_metric( $metric_slug, array $args ) {
 	 * @param string $metric_slug The metric slug.
 	 * @return bool True if registered, false otherwise.
 	 */
-	public function has_registered_metric( $metric_slug ) {
+	public function has_registered_metric( string $metric_slug ): bool {
 		return isset( $this->registered_metrics[ $metric_slug ] ) && isset( $this->registered_metrics_data[ $metric_slug ] );
 	}
 
@@ -127,7 +127,7 @@ public function has_registered_metric( $metric_slug ) {
 	 *
 	 * @since 1.8.0
 	 */
-	public function send_header() {
+	public function send_header(): void {
 		if ( headers_sent() ) {
 			_doing_it_wrong(
 				__METHOD__,
@@ -161,7 +161,7 @@ public function send_header() {
 	 *
 	 * @return string The Server-Timing header value.
 	 */
-	public function get_header() {
+	public function get_header(): string {
 		// Get all metric header values, as long as the current user has access to the metric.
 		$metric_header_values = array_filter(
 			array_map(
@@ -187,14 +187,14 @@ static function ( $value ) {
 	 * Returns whether an output buffer should be used to gather Server-Timing metrics during template rendering.
 	 *
 	 * Without an output buffer, it is only possible to cover metrics from before serving the template, i.e. before
-	 * the HTML output starts. Therefore sites that would like to gather metrics while serving the template should
+	 * the HTML output starts. Therefore, sites that would like to gather metrics while serving the template should
 	 * enable this via the {@see 'perflab_server_timing_use_output_buffer'} filter.
 	 *
 	 * @since 1.8.0
 	 *
 	 * @return bool True if an output buffer should be used, false otherwise.
 	 */
-	public function use_output_buffer() {
+	public function use_output_buffer(): bool {
 		$options = (array) get_option( PERFLAB_SERVER_TIMING_SETTING, array() );
 		$enabled = ! empty( $options['output_buffering'] );
 
@@ -202,7 +202,7 @@ public function use_output_buffer() {
 		 * Filters whether an output buffer should be used to be able to gather additional Server-Timing metrics.
 		 *
 		 * Without an output buffer, it is only possible to cover metrics from before serving the template, i.e. before
-		 * the HTML output starts. Therefore sites that would like to gather metrics while serving the template should
+		 * the HTML output starts. Therefore, sites that would like to gather metrics while serving the template should
 		 * enable this.
 		 *
 		 * @since 1.8.0
@@ -247,7 +247,7 @@ function ( $output ) {
 	 * @param Perflab_Server_Timing_Metric $metric The metric to format.
 	 * @return string|null Segment for the Server-Timing header, or null if no value set.
 	 */
-	private function format_metric_header_value( Perflab_Server_Timing_Metric $metric ) {
+	private function format_metric_header_value( Perflab_Server_Timing_Metric $metric ): ?string {
 		$value = $metric->get_value();
 
 		// If no value is set, make sure it's just passed through.
diff --git a/includes/server-timing/defaults.php b/includes/server-timing/defaults.php
index d935f1bfed..652c615728 100644
--- a/includes/server-timing/defaults.php
+++ b/includes/server-timing/defaults.php
@@ -22,7 +22,7 @@
  *
  * @since 1.8.0
  */
-function perflab_register_default_server_timing_before_template_metrics() {
+function perflab_register_default_server_timing_before_template_metrics(): void {
 	$calculate_before_template_metrics = static function () {
 		// WordPress execution prior to serving the template.
 		perflab_server_timing_register_metric(
@@ -135,7 +135,7 @@ static function ( $passthrough ) use ( $metric ) {
  *
  * @since 1.8.0
  */
-function perflab_register_default_server_timing_template_metrics() {
+function perflab_register_default_server_timing_template_metrics(): void {
 	// Template-related metrics can only be recorded if output buffering is used.
 	if ( ! perflab_server_timing_use_output_buffer() ) {
 		return;
@@ -225,7 +225,7 @@ static function ( $acc, $query ) {
  *
  * @since 2.6.0
  */
-function perflab_register_additional_server_timing_metrics_from_setting() {
+function perflab_register_additional_server_timing_metrics_from_setting(): void {
 	$options = (array) get_option( PERFLAB_SERVER_TIMING_SETTING, array() );
 
 	$hooks_to_measure = array();
diff --git a/includes/server-timing/load.php b/includes/server-timing/load.php
index 3e789ad3a0..d56a02a2c8 100644
--- a/includes/server-timing/load.php
+++ b/includes/server-timing/load.php
@@ -26,8 +26,10 @@
  * its action hooks as expected.
  *
  * @since 1.8.0
+ *
+ * @return Perflab_Server_Timing
  */
-function perflab_server_timing() {
+function perflab_server_timing(): Perflab_Server_Timing {
 	static $server_timing;
 
 	if ( null === $server_timing ) {
@@ -48,6 +50,8 @@ function perflab_server_timing() {
 
 	return $server_timing;
 }
+
+// @phpstan-ignore-next-line
 add_action( 'wp_loaded', 'perflab_server_timing' );
 
 /**
@@ -57,8 +61,8 @@ function perflab_server_timing() {
  *
  * @since 1.8.0
  *
- * @param string $metric_slug The metric slug.
- * @param array  $args        {
+ * @param string                                                $metric_slug The metric slug.
+ * @param array{measure_callback: callable, access_cap: string} $args        {
  *     Arguments for the metric.
  *
  *     @type callable $measure_callback The callback that initiates calculating the metric value. It will receive
@@ -69,7 +73,7 @@ function perflab_server_timing() {
  *                                      needs to be set to "exist".
  * }
  */
-function perflab_server_timing_register_metric( $metric_slug, array $args ) {
+function perflab_server_timing_register_metric( string $metric_slug, array $args ): void {
 	perflab_server_timing()->register_metric( $metric_slug, $args );
 }
 
@@ -80,7 +84,7 @@ function perflab_server_timing_register_metric( $metric_slug, array $args ) {
  *
  * @return bool True if an output buffer should be used, false otherwise.
  */
-function perflab_server_timing_use_output_buffer() {
+function perflab_server_timing_use_output_buffer(): bool {
 	return perflab_server_timing()->use_output_buffer();
 }
 
@@ -93,9 +97,9 @@ function perflab_server_timing_use_output_buffer() {
  * @param string   $metric_slug The metric slug to use within the Server-Timing header.
  * @param string   $access_cap  Capability required to view the metric. If this is a public metric, this needs to be
  *                              set to "exist".
- * @return callable Callback function that will run $callback and measure its execution time once called.
+ * @return Closure Callback function that will run $callback and measure its execution time once called.
  */
-function perflab_wrap_server_timing( $callback, $metric_slug, $access_cap ) {
+function perflab_wrap_server_timing( callable $callback, string $metric_slug, string $access_cap ): Closure {
 	return static function ( ...$callback_args ) use ( $callback, $metric_slug, $access_cap ) {
 		// Gain access to Perflab_Server_Timing_Metric instance.
 		$server_timing_metric = null;
@@ -133,19 +137,34 @@ function perflab_wrap_server_timing( $callback, $metric_slug, $access_cap ) {
 	};
 }
 
+/**
+ * Gets default value for server timing setting.
+ *
+ * @since n.e.x.t
+ *
+ * @return array{benchmarking_actions: string[], benchmarking_filters: string[], output_buffering: bool} Default value.
+ */
+function perflab_get_server_timing_setting_default_value(): array {
+	return array(
+		'benchmarking_actions' => array(),
+		'benchmarking_filters' => array(),
+		'output_buffering'     => false,
+	);
+}
+
 /**
  * Registers the Server-Timing setting.
  *
  * @since 2.6.0
  */
-function perflab_register_server_timing_setting() {
+function perflab_register_server_timing_setting(): void {
 	register_setting(
 		PERFLAB_SERVER_TIMING_SCREEN,
 		PERFLAB_SERVER_TIMING_SETTING,
 		array(
 			'type'              => 'object',
 			'sanitize_callback' => 'perflab_sanitize_server_timing_setting',
-			'default'           => array(),
+			'default'           => perflab_get_server_timing_setting_default_value(),
 		)
 	);
 }
@@ -156,21 +175,17 @@ function perflab_register_server_timing_setting() {
  *
  * @since 2.6.0
  *
- * @param mixed $value Server-Timing setting value.
- * @return array Sanitized Server-Timing setting value.
+ * @param array|mixed $value Server-Timing setting value.
+ * @return array{benchmarking_actions: string[], benchmarking_filters: string[], output_buffering: bool} Sanitized Server-Timing setting value.
  */
-function perflab_sanitize_server_timing_setting( $value ) {
-	static $allowed_keys = array(
-		'benchmarking_actions' => true,
-		'benchmarking_filters' => true,
-		'output_buffering'     => true,
-	);
-
+function perflab_sanitize_server_timing_setting( $value ): array {
 	if ( ! is_array( $value ) ) {
-		return array();
+		$value = array();
 	}
-
-	$value = array_intersect_key( $value, $allowed_keys );
+	$value = wp_array_slice_assoc(
+		array_merge( perflab_get_server_timing_setting_default_value(), $value ),
+		array_keys( perflab_get_server_timing_setting_default_value() )
+	);
 
 	/*
 	 * Ensure that every element is an indexed array of hook names.
@@ -184,7 +199,7 @@ function perflab_sanitize_server_timing_setting( $value ) {
 			array_unique(
 				array_filter(
 					array_map(
-						static function ( $hookname ) {
+						static function ( $hook_name ) {
 							/*
 							 * Allow any characters except whitespace.
 							 * While most hooks use a limited set of characters, hook names in plugins are not
@@ -194,7 +209,7 @@ static function ( $hookname ) {
 							return preg_replace(
 								'/\s/',
 								'',
-								sanitize_text_field( $hookname )
+								sanitize_text_field( $hook_name )
 							);
 						},
 						$hooks
@@ -204,7 +219,7 @@ static function ( $hookname ) {
 		);
 	}
 
-	$value['output_buffering'] = ! empty( $value['output_buffering'] );
+	$value['output_buffering'] = (bool) $value['output_buffering'];
 
 	return $value;
 }
diff --git a/includes/server-timing/object-cache.copy.php b/includes/server-timing/object-cache.copy.php
index 319483d375..7a4c7f2371 100644
--- a/includes/server-timing/object-cache.copy.php
+++ b/includes/server-timing/object-cache.copy.php
@@ -47,7 +47,7 @@
 	 *
 	 * @since 1.8.0
 	 */
-	function perflab_load_server_timing_api_from_dropin() {
+	function perflab_load_server_timing_api_from_dropin(): void {
 		if ( defined( 'PERFLAB_DISABLE_SERVER_TIMING' ) && PERFLAB_DISABLE_SERVER_TIMING ) {
 			return;
 		}
diff --git a/includes/site-health/audit-autoloaded-options/helper.php b/includes/site-health/audit-autoloaded-options/helper.php
index 9d978a5e54..b5ea785413 100644
--- a/includes/site-health/audit-autoloaded-options/helper.php
+++ b/includes/site-health/audit-autoloaded-options/helper.php
@@ -15,9 +15,9 @@
  *
  * @since 1.0.0
  *
- * @return array
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string} Result.
  */
-function perflab_aao_autoloaded_options_test() {
+function perflab_aao_autoloaded_options_test(): array {
 
 	$autoloaded_options_size  = perflab_aao_autoloaded_options_size();
 	$autoloaded_options_count = count( wp_load_alloptions() );
@@ -73,7 +73,7 @@ function perflab_aao_autoloaded_options_test() {
 	$result['description'] = apply_filters( 'perflab_aao_autoloaded_options_limit_description', $result['description'] );
 
 	$result['actions'] = sprintf(
-	/* translators: 1: HelpHub URL. 2: Link description. */
+		/* translators: 1: HelpHub URL. 2: Link description. */
 		'<p><a target="_blank" href="%1$s">%2$s</a></p>',
 		esc_url( __( 'https://wordpress.org/support/article/optimization/#autoloaded-options', 'performance-lab' ) ),
 		__( 'More info about performance optimization', 'performance-lab' )
@@ -99,7 +99,7 @@ function perflab_aao_autoloaded_options_test() {
  *
  * @return int autoloaded data in bytes.
  */
-function perflab_aao_autoloaded_options_size() {
+function perflab_aao_autoloaded_options_size(): int {
 	global $wpdb;
 
 	$autoload_values = perflab_aao_get_autoload_values_to_autoload();
@@ -122,9 +122,9 @@ function perflab_aao_autoloaded_options_size() {
  *
  * @global wpdb $wpdb WordPress database abstraction object.
  *
- * @return array Autoloaded data as option names and their sizes.
+ * @return array<string, object{option_name: string, option_value_length: int}> Autoloaded data as option names and their sizes.
  */
-function perflab_aao_query_autoloaded_options() {
+function perflab_aao_query_autoloaded_options(): array {
 	global $wpdb;
 
 	/**
@@ -161,7 +161,7 @@ function perflab_aao_query_autoloaded_options() {
  *
  * @return string HTML formatted table.
  */
-function perflab_aao_get_autoloaded_options_table() {
+function perflab_aao_get_autoloaded_options_table(): string {
 	$autoload_summary = perflab_aao_query_autoloaded_options();
 
 	$html_table = sprintf(
@@ -201,7 +201,7 @@ function perflab_aao_get_autoloaded_options_table() {
  *
  * @return string HTML formatted table.
  */
-function perflab_aao_get_disabled_autoloaded_options_table() {
+function perflab_aao_get_disabled_autoloaded_options_table(): string {
 	global $wpdb;
 
 	$disabled_options = get_option( 'perflab_aao_disabled_options', array() );
@@ -254,9 +254,9 @@ function perflab_aao_get_disabled_autoloaded_options_table() {
  *
  * @since 3.0.0
  *
- * @return array List of autoload values.
+ * @return string[] List of autoload values.
  */
-function perflab_aao_get_autoload_values_to_autoload() {
+function perflab_aao_get_autoload_values_to_autoload(): array {
 	if ( function_exists( 'wp_autoload_values_to_autoload' ) ) {
 		return wp_autoload_values_to_autoload();
 	}
diff --git a/includes/site-health/audit-autoloaded-options/hooks.php b/includes/site-health/audit-autoloaded-options/hooks.php
index 978ffbd5b0..d6e75fa065 100644
--- a/includes/site-health/audit-autoloaded-options/hooks.php
+++ b/includes/site-health/audit-autoloaded-options/hooks.php
@@ -15,10 +15,10 @@
  *
  * @since 1.0.0
  *
- * @param array $tests Site Health Tests.
- * @return array
+ * @param array{direct: array<string, array{label: string, test: string}>} $tests Site Health Tests.
+ * @return array{direct: array<string, array{label: string, test: string}>} Amended tests.
  */
-function perflab_aao_add_autoloaded_options_test( $tests ) {
+function perflab_aao_add_autoloaded_options_test( array $tests ): array {
 	$tests['direct']['autoloaded_options'] = array(
 		'label' => __( 'Autoloaded options', 'performance-lab' ),
 		'test'  => 'perflab_aao_autoloaded_options_test',
@@ -32,7 +32,7 @@ function perflab_aao_add_autoloaded_options_test( $tests ) {
  *
  * @since 3.0.0
  */
-function perflab_aao_register_admin_actions() {
+function perflab_aao_register_admin_actions(): void {
 	add_action( 'admin_action_perflab_aao_update_autoload', 'perflab_aao_handle_update_autoload' );
 }
 add_action( 'admin_init', 'perflab_aao_register_admin_actions' );
@@ -42,7 +42,7 @@ function perflab_aao_register_admin_actions() {
  *
  * @since 3.0.0
  */
-function perflab_aao_handle_update_autoload() {
+function perflab_aao_handle_update_autoload(): void {
 	check_admin_referer( 'perflab_aao_update_autoload' );
 
 	if ( ! isset( $_GET['option_name'], $_GET['autoload'] ) ) {
@@ -50,7 +50,7 @@ function perflab_aao_handle_update_autoload() {
 	}
 
 	$option_name = sanitize_text_field( wp_unslash( $_GET['option_name'] ) );
-	$autoload    = isset( $_GET['autoload'] ) ? rest_sanitize_boolean( $_GET['autoload'] ) : false;
+	$autoload    = rest_sanitize_boolean( $_GET['autoload'] );
 
 	if ( ! current_user_can( 'manage_options' ) ) {
 		wp_die( esc_html__( 'Permission denied.', 'performance-lab' ) );
@@ -96,7 +96,7 @@ function perflab_aao_handle_update_autoload() {
  *
  * @global string $pagenow The filename of the current screen.
  */
-function perflab_aao_admin_notices() {
+function perflab_aao_admin_notices(): void {
 	if ( 'site-health.php' !== $GLOBALS['pagenow'] ) {
 		return;
 	}
diff --git a/includes/site-health/audit-enqueued-assets/helper.php b/includes/site-health/audit-enqueued-assets/helper.php
index dba449cdb7..e0088c918a 100644
--- a/includes/site-health/audit-enqueued-assets/helper.php
+++ b/includes/site-health/audit-enqueued-assets/helper.php
@@ -15,15 +15,18 @@
  *
  * @since 1.0.0
  *
- * @return array
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string}|array{omitted: true} Result.
  */
-function perflab_aea_enqueued_js_assets_test() {
+function perflab_aea_enqueued_js_assets_test(): array {
 	/**
 	 * If the test didn't run yet, deactivate.
 	 */
 	$enqueued_scripts = perflab_aea_get_total_enqueued_scripts();
 	if ( false === $enqueued_scripts ) {
-		return array();
+		// The return value is validated in JavaScript at:
+		// <https://github.com/WordPress/wordpress-develop/blob/d1e0a6241dcc34f4a5ed464a741116461a88d43b/src/js/_enqueues/admin/site-health.js#L65-L114>
+		// If the value lacks the required keys of test, label, and description then it is omitted.
+		return array( 'omitted' => true );
 	}
 
 	$result = array(
@@ -109,15 +112,16 @@ function perflab_aea_enqueued_js_assets_test() {
  *
  * @since 1.0.0
  *
- * @return array
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string}|array{omitted: true} Result.
  */
-function perflab_aea_enqueued_css_assets_test() {
-	/**
-	 * If the test didn't run yet, deactivate.
-	 */
+function perflab_aea_enqueued_css_assets_test(): array {
+	// Omit if the test didn't run yet, omit.
 	$enqueued_styles = perflab_aea_get_total_enqueued_styles();
 	if ( false === $enqueued_styles ) {
-		return array();
+		// The return value is validated in JavaScript at:
+		// <https://github.com/WordPress/wordpress-develop/blob/d1e0a6241dcc34f4a5ed464a741116461a88d43b/src/js/_enqueues/admin/site-health.js#L65-L114>
+		// If the value lacks the required keys of test, label, and description then it is omitted.
+		return array( 'omitted' => true );
 	}
 	$result = array(
 		'label'       => __( 'Enqueued styles', 'performance-lab' ),
@@ -276,7 +280,7 @@ function perflab_aea_get_total_size_bytes_enqueued_styles() {
  * @param string $resource_url URl resource link.
  * @return string Returns absolute path to the resource.
  */
-function perflab_aea_get_path_from_resource_url( $resource_url ) {
+function perflab_aea_get_path_from_resource_url( string $resource_url ): string {
 	if ( ! $resource_url ) {
 		return '';
 	}
diff --git a/includes/site-health/audit-enqueued-assets/hooks.php b/includes/site-health/audit-enqueued-assets/hooks.php
index 492769b030..fb0238678b 100644
--- a/includes/site-health/audit-enqueued-assets/hooks.php
+++ b/includes/site-health/audit-enqueued-assets/hooks.php
@@ -19,7 +19,7 @@
  *
  * @global WP_Scripts $wp_scripts
  */
-function perflab_aea_audit_enqueued_scripts() {
+function perflab_aea_audit_enqueued_scripts(): void {
 	if ( ! is_admin() && is_front_page() && current_user_can( 'view_site_health_checks' ) && false === get_transient( 'aea_enqueued_front_page_scripts' ) ) {
 		global $wp_scripts;
 		$enqueued_scripts = array();
@@ -64,7 +64,7 @@ function perflab_aea_audit_enqueued_scripts() {
  *
  * @global WP_Styles $wp_styles The WP_Styles current instance.
  */
-function perflab_aea_audit_enqueued_styles() {
+function perflab_aea_audit_enqueued_styles(): void {
 	if ( ! is_admin() && is_front_page() && current_user_can( 'view_site_health_checks' ) && false === get_transient( 'aea_enqueued_front_page_styles' ) ) {
 		global $wp_styles;
 		$enqueued_styles = array();
@@ -108,10 +108,10 @@ function perflab_aea_audit_enqueued_styles() {
  *
  * @since 1.0.0
  *
- * @param array $tests Site Health Tests.
- * @return array
+ * @param array{direct: array<string, array{label: string, test: string}>} $tests Site Health Tests.
+ * @return array{direct: array<string, array{label: string, test: string}>} Amended tests.
  */
-function perflab_aea_add_enqueued_assets_test( $tests ) {
+function perflab_aea_add_enqueued_assets_test( array $tests ): array {
 	$tests['direct']['enqueued_js_assets']  = array(
 		'label' => __( 'JS assets', 'performance-lab' ),
 		'test'  => 'perflab_aea_enqueued_js_assets_test',
@@ -131,7 +131,7 @@ function perflab_aea_add_enqueued_assets_test( $tests ) {
  *
  * @since 1.0.0
  */
-function perflab_aea_clean_aea_audit_action() {
+function perflab_aea_clean_aea_audit_action(): void {
 	if ( isset( $_GET['action'] ) && 'clean_aea_audit' === $_GET['action'] && current_user_can( 'view_site_health_checks' ) ) {
 		check_admin_referer( 'clean_aea_audit' );
 		perflab_aea_invalidate_cache_transients();
@@ -145,7 +145,7 @@ function perflab_aea_clean_aea_audit_action() {
  *
  * @since 1.0.0
  */
-function perflab_aea_invalidate_cache_transients() {
+function perflab_aea_invalidate_cache_transients(): void {
 	delete_transient( 'aea_enqueued_front_page_scripts' );
 	delete_transient( 'aea_enqueued_front_page_styles' );
 }
diff --git a/includes/site-health/avif-support/helper.php b/includes/site-health/avif-support/helper.php
index 214cd1f546..4dcaff903f 100644
--- a/includes/site-health/avif-support/helper.php
+++ b/includes/site-health/avif-support/helper.php
@@ -15,9 +15,9 @@
  *
  * @since n.e.x.t
  *
- * @return array
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string} Result.
  */
-function avif_uploads_check_avif_supported_test() {
+function avif_uploads_check_avif_supported_test(): array {
 	$result = array(
 		'label'       => __( 'Your site supports AVIF', 'performance-lab' ),
 		'status'      => 'good',
diff --git a/includes/site-health/avif-support/hooks.php b/includes/site-health/avif-support/hooks.php
index 63b7d813ed..d338f85990 100644
--- a/includes/site-health/avif-support/hooks.php
+++ b/includes/site-health/avif-support/hooks.php
@@ -15,10 +15,10 @@
  *
  * @since n.e.x.t
  *
- * @param array $tests Site Health Tests.
- * @return array
+ * @param array{direct: array<string, array{label: string, test: string}>} $tests Site Health Tests.
+ * @return array{direct: array<string, array{label: string, test: string}>} Amended tests.
  */
-function avif_uploads_add_is_avif_supported_test( $tests ) {
+function avif_uploads_add_is_avif_supported_test( array $tests ): array {
 	$tests['direct']['avif_supported'] = array(
 		'label' => __( 'AVIF Support', 'performance-lab' ),
 		'test'  => 'avif_uploads_check_avif_supported_test',
diff --git a/includes/site-health/webp-support/helper.php b/includes/site-health/webp-support/helper.php
index ab09bb2a2e..029d50abdc 100644
--- a/includes/site-health/webp-support/helper.php
+++ b/includes/site-health/webp-support/helper.php
@@ -15,9 +15,9 @@
  *
  * @since 1.0.0
  *
- * @return array
+ * @return array{label: string, status: string, badge: array{label: string, color: string}, description: string, actions: string, test: string} Result.
  */
-function webp_uploads_check_webp_supported_test() {
+function webp_uploads_check_webp_supported_test(): array {
 	$result = array(
 		'label'       => __( 'Your site supports WebP', 'performance-lab' ),
 		'status'      => 'good',
diff --git a/includes/site-health/webp-support/hooks.php b/includes/site-health/webp-support/hooks.php
index 67a757e415..d00397cf60 100644
--- a/includes/site-health/webp-support/hooks.php
+++ b/includes/site-health/webp-support/hooks.php
@@ -15,10 +15,10 @@
  *
  * @since 1.0.0
  *
- * @param array $tests Site Health Tests.
- * @return array
+ * @param array{direct: array<string, array{label: string, test: string}>} $tests Site Health Tests.
+ * @return array{direct: array<string, array{label: string, test: string}>} Amended tests.
  */
-function webp_uploads_add_is_webp_supported_test( $tests ) {
+function webp_uploads_add_is_webp_supported_test( array $tests ): array {
 	$tests['direct']['webp_supported'] = array(
 		'label' => __( 'WebP Support', 'performance-lab' ),
 		'test'  => 'webp_uploads_check_webp_supported_test',
diff --git a/load.php b/load.php
index 7a6d8b52c5..5140c42893 100644
--- a/load.php
+++ b/load.php
@@ -48,7 +48,7 @@
  * @since 2.9.0 The generator tag now includes the active standalone plugin slugs.
  * @since 3.0.0 The generator tag no longer includes module slugs.
  */
-function perflab_get_generator_content() {
+function perflab_get_generator_content(): string {
 	$active_plugins = array();
 	foreach ( perflab_get_standalone_plugin_version_constants() as $plugin_slug => $constant_name ) {
 		if ( defined( $constant_name ) && ! str_starts_with( constant( $constant_name ), 'Performance Lab ' ) ) {
@@ -71,7 +71,7 @@ function perflab_get_generator_content() {
  *
  * @since 1.1.0
  */
-function perflab_render_generator() {
+function perflab_render_generator(): void {
 	$content = perflab_get_generator_content();
 
 	echo '<meta name="generator" content="' . esc_attr( $content ) . '">' . "\n";
@@ -85,7 +85,7 @@ function perflab_render_generator() {
  *
  * @return array<string, array{'constant': string, 'experimental'?: bool}> Associative array of $plugin_slug => $plugin_data pairs.
  */
-function perflab_get_standalone_plugin_data() {
+function perflab_get_standalone_plugin_data(): array {
 	/*
 	 * Alphabetically sorted list of plugin slugs and their data.
 	 * Supported keys per plugin are:
@@ -125,7 +125,7 @@ function perflab_get_standalone_plugin_data() {
  *
  * @return array<string, string> Map of plugin slug and the version constant used.
  */
-function perflab_get_standalone_plugin_version_constants() {
+function perflab_get_standalone_plugin_version_constants(): array {
 	return wp_list_pluck( perflab_get_standalone_plugin_data(), 'constant' );
 }
 
@@ -144,7 +144,7 @@ function perflab_get_standalone_plugin_version_constants() {
  *
  * @global WP_Filesystem_Base $wp_filesystem WordPress filesystem subclass.
  */
-function perflab_maybe_set_object_cache_dropin() {
+function perflab_maybe_set_object_cache_dropin(): void {
 	global $wp_filesystem;
 
 	// Bail if Server-Timing is disabled entirely.
@@ -255,7 +255,7 @@ function perflab_maybe_set_object_cache_dropin() {
  *
  * @global WP_Filesystem_Base $wp_filesystem WordPress filesystem subclass.
  */
-function perflab_maybe_remove_object_cache_dropin() {
+function perflab_maybe_remove_object_cache_dropin(): void {
 	global $wp_filesystem;
 
 	// Bail if disabled via constant.
@@ -298,7 +298,7 @@ function perflab_maybe_remove_object_cache_dropin() {
  *
  * @global $plugin_page
  */
-function perflab_no_access_redirect_module_to_performance_feature_page() {
+function perflab_no_access_redirect_module_to_performance_feature_page(): void {
 	global $plugin_page;
 
 	if ( 'perflab-modules' !== $plugin_page ) {
@@ -319,7 +319,7 @@ function perflab_no_access_redirect_module_to_performance_feature_page() {
  *
  * @since 3.0.0
  */
-function perflab_cleanup_option() {
+function perflab_cleanup_option(): void {
 	if ( current_user_can( 'manage_options' ) ) {
 		delete_option( 'perflab_modules_settings' );
 	}
diff --git a/tests/includes/server-timing/load-tests.php b/tests/includes/server-timing/load-tests.php
index dcffb6ccdc..fa3b132144 100644
--- a/tests/includes/server-timing/load-tests.php
+++ b/tests/includes/server-timing/load-tests.php
@@ -59,6 +59,11 @@ public function test_perflab_wrap_server_timing() {
 		$this->assertSame( 123, $wrapped(), 'Calling wrapped callback multiple times should not result in warning' );
 	}
 
+	/**
+	 * @covers ::perflab_get_server_timing_setting_default_value
+	 * @covers ::perflab_register_server_timing_setting
+	 * @covers ::perflab_sanitize_server_timing_setting
+	 */
 	public function test_perflab_register_server_timing_setting() {
 		global $new_allowed_options, $wp_registered_settings;
 
@@ -76,12 +81,19 @@ public function test_perflab_register_server_timing_setting() {
 		$this->assertTrue( isset( $new_allowed_options[ PERFLAB_SERVER_TIMING_SCREEN ] ) );
 		$this->assertSame( array( PERFLAB_SERVER_TIMING_SETTING ), $new_allowed_options[ PERFLAB_SERVER_TIMING_SCREEN ] );
 
+		$expected_default = array(
+			'benchmarking_actions' => array(),
+			'benchmarking_filters' => array(),
+			'output_buffering'     => false,
+		);
+		$this->assertSame( $expected_default, perflab_get_server_timing_setting_default_value() );
+
 		// Assert that registered default works correctly.
-		$this->assertSame( array(), get_option( PERFLAB_SERVER_TIMING_SETTING ) );
+		$this->assertSame( $expected_default, get_option( PERFLAB_SERVER_TIMING_SETTING ) );
 
 		// Assert that most basic sanitization works correctly (an array is required).
 		update_option( PERFLAB_SERVER_TIMING_SETTING, 'invalid' );
-		$this->assertSame( array(), get_option( PERFLAB_SERVER_TIMING_SETTING ) );
+		$this->assertSame( $expected_default, get_option( PERFLAB_SERVER_TIMING_SETTING ) );
 	}
 
 	/**
@@ -96,74 +108,104 @@ public function test_perflab_sanitize_server_timing_setting( $unsanitized, $expe
 	}
 
 	public function data_perflab_sanitize_server_timing_setting() {
+		$default = array(
+			'benchmarking_actions' => array(),
+			'benchmarking_filters' => array(),
+			'output_buffering'     => false,
+		);
+
 		return array(
 			'invalid type'                                => array(
 				'invalid',
-				array(),
+				$default,
 			),
 			'empty list, array'                           => array(
 				array( 'benchmarking_actions' => array() ),
-				array(
-					'benchmarking_actions' => array(),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array(),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'empty list, string'                          => array(
 				array( 'benchmarking_actions' => '' ),
-				array(
-					'benchmarking_actions' => array(),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array(),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'empty list, string with whitespace'          => array(
 				array( 'benchmarking_actions' => ' ' ),
-				array(
-					'benchmarking_actions' => array(),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array(),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'regular list, array'                         => array(
 				array( 'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ) ),
-				array(
-					'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'regular list, string'                        => array(
 				array( 'benchmarking_actions' => "after_setup_theme\ninit\nwp_loaded" ),
-				array(
-					'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'regular list, string with whitespace'        => array(
 				array( 'benchmarking_actions' => "after_setup_  theme \ninit \n\nwp_loaded\n" ),
-				array(
-					'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'regular list, array with duplicates'         => array(
 				array( 'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded', 'init' ) ),
-				array(
-					'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array( 'after_setup_theme', 'init', 'wp_loaded' ),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'regular list, array with special hook chars' => array(
 				array( 'benchmarking_actions' => array( 'namespace/hookname', 'namespace.hookname' ) ),
-				array(
-					'benchmarking_actions' => array( 'namespace/hookname', 'namespace.hookname' ),
-					'output_buffering'     => false,
+				array_merge(
+					$default,
+					array(
+						'benchmarking_actions' => array( 'namespace/hookname', 'namespace.hookname' ),
+						'output_buffering'     => false,
+					)
 				),
 			),
 			'output buffering enabled'                    => array(
 				array( 'output_buffering' => 'on' ),
-				array( 'output_buffering' => true ),
+				array_merge( $default, array( 'output_buffering' => true ) ),
 			),
 			'regular list, disallowed key'                => array(
 				array( 'not_allowed' => array( 'after_setup_theme', 'init', 'wp_loaded' ) ),
-				array( 'output_buffering' => false ),
+				array_merge( $default, array( 'output_buffering' => false ) ),
 			),
 		);
 	}
diff --git a/tests/includes/site-health/audit-enqueued-assets/audit-enqueued-assets-test.php b/tests/includes/site-health/audit-enqueued-assets/audit-enqueued-assets-test.php
index e0baf01c59..569d3b4eb3 100644
--- a/tests/includes/site-health/audit-enqueued-assets/audit-enqueued-assets-test.php
+++ b/tests/includes/site-health/audit-enqueued-assets/audit-enqueued-assets-test.php
@@ -175,7 +175,7 @@ public function test_perflab_aea_add_enqueued_assets_test() {
 	 * Test perflab_aea_enqueued_js_assets_test() no transient saved.
 	 */
 	public function test_perflab_aea_enqueued_js_assets_test_no_transient() {
-		$this->assertEqualSets( array(), perflab_aea_enqueued_js_assets_test() );
+		$this->assertSame( array( 'omitted' => true ), perflab_aea_enqueued_js_assets_test() );
 	}
 
 	/**
@@ -200,7 +200,7 @@ public function test_perflab_aea_enqueued_js_assets_test_with_assets_more_than_t
 	 * Test perflab_aea_enqueued_css_assets_test() no transient saved.
 	 */
 	public function test_perflab_aea_enqueued_css_assets_test_no_transient() {
-		$this->assertEqualSets( array(), perflab_aea_enqueued_css_assets_test() );
+		$this->assertSame( array( 'omitted' => true ), perflab_aea_enqueued_css_assets_test() );
 	}
 
 	/**

From 51d1894cf4cc7c2b59c7f293058b722b4870c0fa Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 3 May 2024 09:34:51 -0700
Subject: [PATCH 2/5] Remove paths from ignoreErrors for str functions

---
 bin/phpstan/constants.php |  2 +-
 phpstan.neon.dist         | 14 +++-----------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/bin/phpstan/constants.php b/bin/phpstan/constants.php
index 71adeef274..1f5e05b50c 100644
--- a/bin/phpstan/constants.php
+++ b/bin/phpstan/constants.php
@@ -2,7 +2,7 @@
 /**
  * Constants for PHPStan static analysis.
  *
- * @package speculation-rules
+ * @package performance-lab
  */
 
 define( 'SPECULATION_RULES_VERSION', '0.0.0' );
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index aa5d3d3213..31ee0d462a 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -15,16 +15,8 @@ parameters:
 		- vendor/wp-phpunit/wp-phpunit/
 	dynamicConstantNames:
 		- PERFLAB_OBJECT_CACHE_DROPIN_VERSION
+	reportUnmatchedIgnoredErrors: false
 	ignoreErrors:
 		# False positive as WordPress ships with a polyfill.
-		-
-			message: "#^Function str_starts_with not found\\.$#"
-			paths:
-				- load.php
-				- plugins/optimization-detective/optimization.php
-				- plugins/speculation-rules/class-plsr-url-pattern-prefixer.php
-		-
-			message: "#^Function str_contains not found\\.$#"
-			paths:
-				- plugins/auto-sizes/hooks.php
-				- plugins/dominant-color-images/hooks.php
+		- "#^Function str_starts_with not found\\.$#"
+		- "#^Function str_contains not found\\.$#"

From 2cb9ab0ef7deb4173ec89193d473e25b9345f3e0 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 3 May 2024 10:30:36 -0700
Subject: [PATCH 3/5] Eliminate ignoreErrors in favor of adding compat stubs

---
 bin/phpstan/functions.stub | 38 ++++++++++++++++++++++++++++++++++++++
 phpstan.neon.dist          |  7 ++-----
 2 files changed, 40 insertions(+), 5 deletions(-)
 create mode 100644 bin/phpstan/functions.stub

diff --git a/bin/phpstan/functions.stub b/bin/phpstan/functions.stub
new file mode 100644
index 0000000000..dbf94c0139
--- /dev/null
+++ b/bin/phpstan/functions.stub
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Function stubs for PHPStan static analysis.
+ *
+ * @package performance-lab
+ */
+
+if ( ! function_exists( 'str_contains' ) ) {
+	/**
+	 * Polyfill for `str_contains()` function added in PHP 8.0.
+	 *
+	 * Performs a case-sensitive check indicating if needle is
+	 * contained in haystack.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @param string $haystack The string to search in.
+	 * @param string $needle   The substring to search for in the `$haystack`.
+	 * @return bool True if `$needle` is in `$haystack`, otherwise false.
+	 */
+	function str_contains( string $haystack, string $needle ): bool {}
+}
+
+if ( ! function_exists( 'str_starts_with' ) ) {
+	/**
+	 * Polyfill for `str_starts_with()` function added in PHP 8.0.
+	 *
+	 * Performs a case-sensitive check indicating if
+	 * the haystack begins with needle.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @param string $haystack The string to search in.
+	 * @param string $needle   The substring to search for in the `$haystack`.
+	 * @return bool True if `$haystack` starts with `$needle`, otherwise false.
+	 */
+	function str_starts_with( string $haystack, string $needle ): bool {}
+}
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 31ee0d462a..2116e3f289 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -13,10 +13,7 @@ parameters:
 		- plugins/webp-uploads/load.php
 	scanDirectories:
 		- vendor/wp-phpunit/wp-phpunit/
+	scanFiles:
+		- bin/phpstan/functions.stub
 	dynamicConstantNames:
 		- PERFLAB_OBJECT_CACHE_DROPIN_VERSION
-	reportUnmatchedIgnoredErrors: false
-	ignoreErrors:
-		# False positive as WordPress ships with a polyfill.
-		- "#^Function str_starts_with not found\\.$#"
-		- "#^Function str_contains not found\\.$#"

From 828c87fef5154e9207502ed3842c2b535018fa64 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 3 May 2024 12:03:38 -0700
Subject: [PATCH 4/5] Reuse php-8-stubs instead of adding our own

---
 bin/phpstan/functions.stub | 38 --------------------------------------
 composer.json              |  3 ++-
 composer.lock              | 34 +++++++++++++++++++++++++++++++++-
 phpstan.neon.dist          |  5 ++++-
 4 files changed, 39 insertions(+), 41 deletions(-)
 delete mode 100644 bin/phpstan/functions.stub

diff --git a/bin/phpstan/functions.stub b/bin/phpstan/functions.stub
deleted file mode 100644
index dbf94c0139..0000000000
--- a/bin/phpstan/functions.stub
+++ /dev/null
@@ -1,38 +0,0 @@
-<?php
-/**
- * Function stubs for PHPStan static analysis.
- *
- * @package performance-lab
- */
-
-if ( ! function_exists( 'str_contains' ) ) {
-	/**
-	 * Polyfill for `str_contains()` function added in PHP 8.0.
-	 *
-	 * Performs a case-sensitive check indicating if needle is
-	 * contained in haystack.
-	 *
-	 * @since 5.9.0
-	 *
-	 * @param string $haystack The string to search in.
-	 * @param string $needle   The substring to search for in the `$haystack`.
-	 * @return bool True if `$needle` is in `$haystack`, otherwise false.
-	 */
-	function str_contains( string $haystack, string $needle ): bool {}
-}
-
-if ( ! function_exists( 'str_starts_with' ) ) {
-	/**
-	 * Polyfill for `str_starts_with()` function added in PHP 8.0.
-	 *
-	 * Performs a case-sensitive check indicating if
-	 * the haystack begins with needle.
-	 *
-	 * @since 5.9.0
-	 *
-	 * @param string $haystack The string to search in.
-	 * @param string $needle   The substring to search for in the `$haystack`.
-	 * @return bool True if `$haystack` starts with `$needle`, otherwise false.
-	 */
-	function str_starts_with( string $haystack, string $needle ): bool {}
-}
diff --git a/composer.json b/composer.json
index 56aeace8fd..25925b5fcb 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,8 @@
     "szepeviktor/phpstan-wordpress": "^1.3",
     "wp-coding-standards/wpcs": "^3.1",
     "wp-phpunit/wp-phpunit": "^6.5",
-    "yoast/phpunit-polyfills": "^1.0"
+    "yoast/phpunit-polyfills": "^1.0",
+    "phpstan/php-8-stubs": "^0.3.84"
   },
   "autoload-dev": {
     "psr-4": {
diff --git a/composer.lock b/composer.lock
index 877e086bc3..174cb2a9e3 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "2fe7239c502769a6dbb477a761e93ded",
+    "content-hash": "d924800b9c7a182fa46bd0ef6c685361",
     "packages": [],
     "packages-dev": [
         {
@@ -651,6 +651,38 @@
             },
             "time": "2023-05-24T08:59:17+00:00"
         },
+        {
+            "name": "phpstan/php-8-stubs",
+            "version": "0.3.84",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/php-8-stubs.git",
+                "reference": "d713e9c3f6f8223d323efe9558b477ae92e989df"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/php-8-stubs/zipball/d713e9c3f6f8223d323efe9558b477ae92e989df",
+                "reference": "d713e9c3f6f8223d323efe9558b477ae92e989df",
+                "shasum": ""
+            },
+            "type": "library",
+            "autoload": {
+                "classmap": [
+                    "Php8StubsMap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT",
+                "PHP-3.01"
+            ],
+            "description": "PHP stubs extracted from php-src",
+            "support": {
+                "issues": "https://github.com/phpstan/php-8-stubs/issues",
+                "source": "https://github.com/phpstan/php-8-stubs/tree/0.3.84"
+            },
+            "time": "2023-12-30T11:29:15+00:00"
+        },
         {
             "name": "phpstan/phpdoc-parser",
             "version": "1.28.0",
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 2116e3f289..e007ff9f40 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -14,6 +14,9 @@ parameters:
 	scanDirectories:
 		- vendor/wp-phpunit/wp-phpunit/
 	scanFiles:
-		- bin/phpstan/functions.stub
+		# These are needed due config.platform.php being 7.2 in composer.json and wordpress-stubs not including polyfills.
+		# See <https://github.com/php-stubs/wordpress-stubs/issues/100>.
+		- vendor/phpstan/php-8-stubs/stubs/ext/standard/str_contains.php
+		- vendor/phpstan/php-8-stubs/stubs/ext/standard/str_starts_with.php
 	dynamicConstantNames:
 		- PERFLAB_OBJECT_CACHE_DROPIN_VERSION

From 5e4cb3b0e32e39f1d8cfb68ec35ef68d978de13b Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 3 May 2024 12:44:23 -0700
Subject: [PATCH 5/5] Fix test_od_optimize_template_output_buffer

---
 tests/plugins/optimization-detective/optimization-tests.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/plugins/optimization-detective/optimization-tests.php b/tests/plugins/optimization-detective/optimization-tests.php
index d5728af49b..8a153f9136 100644
--- a/tests/plugins/optimization-detective/optimization-tests.php
+++ b/tests/plugins/optimization-detective/optimization-tests.php
@@ -1077,7 +1077,7 @@ static function () {
 						  <title>XHTML 1.0 Strict Example</title>
 						</head>
 						<body>
-							<p><img data-od-xpath="/*[0][self::HTML]/*[1][self::BODY]/*[0][self::P]/*[0][self::IMG]" src="https://example.com/foo.jpg" alt="Foo" width="1200" height="800" /></p>
+							<p><img data-od-xpath="/*[1][self::HTML]/*[2][self::BODY]/*[1][self::P]/*[1][self::IMG]" src="https://example.com/foo.jpg" alt="Foo" width="1200" height="800" /></p>
 							<script type="module">/* import detect ... */</script>
 						</body>
 					</html>