diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 63bf993..bcefae6 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -10,13 +10,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [7.3, 7.4, 8.0]
+        php: [7.3, 7.4, 8.0, 8.1]
         experimental: [false]
         include:
-          - php: 8.0
-            analysis: true
           - php: 8.1
-            experimental: true
+            analysis: true
 
     steps:
       - name: Checkout
diff --git a/composer.json b/composer.json
index 816775f..75a07bf 100644
--- a/composer.json
+++ b/composer.json
@@ -42,7 +42,7 @@
     "php-http/psr7-integration-tests": "dev-master",
     "phpspec/prophecy": "^1.14",
     "phpspec/prophecy-phpunit": "^2.0",
-    "phpstan/phpstan": "^0.12.99",
+    "phpstan/phpstan": "^1.0",
     "phpunit/phpunit": "^9.5",
     "squizlabs/php_codesniffer": "^3.6"
   },
diff --git a/src/Cookies.php b/src/Cookies.php
index 894bdb1..00448a2 100644
--- a/src/Cookies.php
+++ b/src/Cookies.php
@@ -193,7 +193,7 @@ protected function toHeader(string $name, array $properties): string
     public static function parseHeader($header): array
     {
         if (is_array($header)) {
-            $header = isset($header[0]) ? $header[0] : '';
+            $header = $header[0] ?? '';
         }
 
         if (!is_string($header)) {
diff --git a/src/Factory/ServerRequestFactory.php b/src/Factory/ServerRequestFactory.php
index 55ffd8f..b6e0471 100644
--- a/src/Factory/ServerRequestFactory.php
+++ b/src/Factory/ServerRequestFactory.php
@@ -92,7 +92,7 @@ public function createServerRequest(string $method, $uri, array $serverParams =
      */
     public static function createFromGlobals(): Request
     {
-        $method = isset($_SERVER['REQUEST_METHOD']) ? $_SERVER['REQUEST_METHOD'] : 'GET';
+        $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
         $uri = (new UriFactory())->createFromGlobals($_SERVER);
 
         $headers = Headers::createFromGlobals();
@@ -106,7 +106,7 @@ public static function createFromGlobals(): Request
         $uploadedFiles = UploadedFile::createFromGlobals($_SERVER);
 
         $request = new Request($method, $uri, $headers, $cookies, $_SERVER, $body, $uploadedFiles);
-        $contentTypes = $request->getHeader('Content-Type') ?? [];
+        $contentTypes = $request->getHeader('Content-Type');
 
         $parsedContentType = '';
         foreach ($contentTypes as $contentType) {
diff --git a/src/Factory/UriFactory.php b/src/Factory/UriFactory.php
index 7f0a216..11bc7c3 100644
--- a/src/Factory/UriFactory.php
+++ b/src/Factory/UriFactory.php
@@ -62,12 +62,12 @@ public function createUri(string $uri = ''): UriInterface
     public function createFromGlobals(array $globals): Uri
     {
         // Scheme
-        $https = isset($globals['HTTPS']) ? $globals['HTTPS'] : false;
+        $https = $globals['HTTPS'] ?? false;
         $scheme = !$https || $https === 'off' ? 'http' : 'https';
 
         // Authority: Username and password
-        $username = isset($globals['PHP_AUTH_USER']) ? $globals['PHP_AUTH_USER'] : '';
-        $password = isset($globals['PHP_AUTH_PW']) ? $globals['PHP_AUTH_PW'] : '';
+        $username = $globals['PHP_AUTH_USER'] ?? '';
+        $password = $globals['PHP_AUTH_PW'] ?? '';
 
         // Authority: Host
         $host = '';
@@ -106,7 +106,7 @@ public function createFromGlobals(array $globals): Uri
             $requestUri = $uriFragments[0];
 
             if ($queryString === '' && count($uriFragments) > 1) {
-                $queryString = parse_url('http://www.example.com' . $globals['REQUEST_URI'], PHP_URL_QUERY) ?? '';
+                $queryString = parse_url('https://www.example.com' . $globals['REQUEST_URI'], PHP_URL_QUERY) ?? '';
             }
         }
 
diff --git a/src/Headers.php b/src/Headers.php
index afde205..355c151 100644
--- a/src/Headers.php
+++ b/src/Headers.php
@@ -191,7 +191,7 @@ protected function parseAuthorizationHeader(array $headers): array
             if (isset($this->globals['REDIRECT_HTTP_AUTHORIZATION'])) {
                 $headers['Authorization'] = $this->globals['REDIRECT_HTTP_AUTHORIZATION'];
             } elseif (isset($this->globals['PHP_AUTH_USER'])) {
-                $pw = isset($this->globals['PHP_AUTH_PW']) ? $this->globals['PHP_AUTH_PW'] : '';
+                $pw = $this->globals['PHP_AUTH_PW'] ?? '';
                 $headers['Authorization'] = 'Basic ' . base64_encode($this->globals['PHP_AUTH_USER'] . ':' . $pw);
             } elseif (isset($this->globals['PHP_AUTH_DIGEST'])) {
                 $headers['Authorization'] = $this->globals['PHP_AUTH_DIGEST'];
diff --git a/src/Request.php b/src/Request.php
index a80329e..3dd3cd8 100644
--- a/src/Request.php
+++ b/src/Request.php
@@ -201,7 +201,7 @@ public function getRequestTarget(): string
      */
     public function withRequestTarget($requestTarget)
     {
-        if (preg_match('#\s#', $requestTarget)) {
+        if (!is_string($requestTarget) || preg_match('#\s#', $requestTarget)) {
             throw new InvalidArgumentException(
                 'Invalid request target provided; must be a string and cannot contain whitespace'
             );
@@ -331,7 +331,7 @@ public function getAttributes(): array
      */
     public function getAttribute($name, $default = null)
     {
-        return isset($this->attributes[$name]) ? $this->attributes[$name] : $default;
+        return $this->attributes[$name] ?? $default;
     }
 
     /**
diff --git a/src/Response.php b/src/Response.php
index 3f5b943..f4688f3 100644
--- a/src/Response.php
+++ b/src/Response.php
@@ -124,8 +124,8 @@ public function __construct(
         ?StreamInterface $body = null
     ) {
         $this->status = $this->filterStatus($status);
-        $this->headers = $headers ? $headers : new Headers([], []);
-        $this->body = $body ? $body : (new StreamFactory())->createStream();
+        $this->headers = $headers ?: new Headers([], []);
+        $this->body = $body ?: (new StreamFactory())->createStream();
     }
 
     /**
diff --git a/src/Stream.php b/src/Stream.php
index 8616989..8f8b318 100644
--- a/src/Stream.php
+++ b/src/Stream.php
@@ -119,7 +119,7 @@ public function getMetadata($key = null)
             return $this->meta;
         }
 
-        return isset($this->meta[$key]) ? $this->meta[$key] : null;
+        return $this->meta[$key] ?? null;
     }
 
     /**
@@ -209,7 +209,7 @@ public function getSize(): ?int
             $stats = fstat($this->stream);
 
             if ($stats) {
-                $this->size = isset($stats['size']) && !$this->isPipe() ? $stats['size'] : null;
+                $this->size = !$this->isPipe() ? $stats['size'] : null;
             }
         }
 
@@ -239,7 +239,7 @@ public function tell(): int
      */
     public function eof(): bool
     {
-        return $this->stream ? feof($this->stream) : true;
+        return !$this->stream || feof($this->stream);
     }
 
     /**
@@ -256,7 +256,7 @@ public function isReadable(): bool
                 if ($this->stream) {
                     $mode = $this->getMetadata('mode');
 
-                    if (strstr($mode, 'r') !== false || strstr($mode, '+') !== false) {
+                    if (is_string($mode) && (strstr($mode, 'r') !== false || strstr($mode, '+') !== false)) {
                         $this->readable = true;
                     }
                 }
@@ -277,7 +277,7 @@ public function isWritable(): bool
             if ($this->stream) {
                 $mode = $this->getMetadata('mode');
 
-                if (strstr($mode, 'w') !== false || strstr($mode, '+') !== false) {
+                if (is_string($mode) && (strstr($mode, 'w') !== false || strstr($mode, '+') !== false)) {
                     $this->writable = true;
                 }
             }
@@ -329,7 +329,7 @@ public function read($length): string
     {
         $data = false;
 
-        if ($this->isReadable() && $this->stream) {
+        if ($this->isReadable() && $this->stream && $length >= 0) {
             $data = fread($this->stream, $length);
         }
 
@@ -410,7 +410,7 @@ public function isPipe(): bool
                 $stats = fstat($this->stream);
 
                 if (is_array($stats)) {
-                    $this->isPipe = isset($stats['mode']) && ($stats['mode'] & self::FSTAT_MODE_S_IFIFO) !== 0;
+                    $this->isPipe = ($stats['mode'] & self::FSTAT_MODE_S_IFIFO) !== 0;
                 }
             }
         }
diff --git a/src/UploadedFile.php b/src/UploadedFile.php
index 568e342..b34109c 100644
--- a/src/UploadedFile.php
+++ b/src/UploadedFile.php
@@ -237,7 +237,7 @@ public static function createFromGlobals(array $globals): array
         }
 
         if (!empty($_FILES)) {
-            return static::parseUploadedFiles($_FILES);
+            return self::parseUploadedFiles($_FILES);
         }
 
         return [];
@@ -258,7 +258,7 @@ private static function parseUploadedFiles(array $uploadedFiles): array
         foreach ($uploadedFiles as $field => $uploadedFile) {
             if (!isset($uploadedFile['error'])) {
                 if (is_array($uploadedFile)) {
-                    $parsed[$field] = static::parseUploadedFiles($uploadedFile);
+                    $parsed[$field] = self::parseUploadedFiles($uploadedFile);
                 }
                 continue;
             }
@@ -267,9 +267,9 @@ private static function parseUploadedFiles(array $uploadedFiles): array
             if (!is_array($uploadedFile['error'])) {
                 $parsed[$field] = new static(
                     $uploadedFile['tmp_name'],
-                    isset($uploadedFile['name']) ? $uploadedFile['name'] : null,
-                    isset($uploadedFile['type']) ? $uploadedFile['type'] : null,
-                    isset($uploadedFile['size']) ? $uploadedFile['size'] : null,
+                    $uploadedFile['name'] ?? null,
+                    $uploadedFile['type'] ?? null,
+                    $uploadedFile['size'] ?? null,
                     $uploadedFile['error'],
                     true
                 );
@@ -283,7 +283,7 @@ private static function parseUploadedFiles(array $uploadedFiles): array
                     $subArray[$fileIdx]['error'] = $uploadedFile['error'][$fileIdx];
                     $subArray[$fileIdx]['size'] = $uploadedFile['size'][$fileIdx];
 
-                    $parsed[$field] = static::parseUploadedFiles($subArray);
+                    $parsed[$field] = self::parseUploadedFiles($subArray);
                 }
             }
         }
diff --git a/src/Uri.php b/src/Uri.php
index a22f38e..4b499cc 100644
--- a/src/Uri.php
+++ b/src/Uri.php
@@ -177,7 +177,7 @@ public function getUserInfo(): string
     {
         $info = $this->user;
 
-        if (isset($this->password) && $this->password !== '') {
+        if ($this->password !== '') {
             $info .= ':' . $this->password;
         }