[5.x] Add to_qs modifier

src/Modifiers/CoreModifiers.php

@@ -2549,6 +2549,16 @@ public function toJson($value, $params)
         return json_encode($value, $options);
     }
 
+    /**
+     * Converts the data to a query string.
+     *
+     * @return string
+     */
+    public function toQs($value)
+    {
+        return Arr::query($value);
+    }
+
     /**
      * Converts each tab in the string to some number of spaces, as defined by
      * $param[0]. By default, each tab is converted to 4 consecutive spaces.

tests/Modifiers/ToQsTest.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Modifiers;
+
+use Statamic\Modifiers\Modify;
+use Tests\PreventSavingStacheItemsToDisk;
+use Tests\TestCase;
+
+class ToQsTest extends TestCase
+{
+    use PreventSavingStacheItemsToDisk;
+
+    /**
+     * @test
+     */
+    public function it_converts_to_query_string(): void
+    {
+        $input = [
+            'mode' => 'plaid',
+            'area' => [51, 52],
+            'hat' => null,
+            'transportation' => [
+                'bike' => true,
+                'delorian' => false,
+            ],
+        ];
+        $modified = $this->modify(value($input));
+
+        $expected = 'mode=plaid&area%5B0%5D=51&area%5B1%5D=52&transportation%5Bbike%5D=1&transportation%5Bdelorian%5D=0';
+        $this->assertEquals($expected, $modified);
+    }
+
+    private function modify($value, $options = [])
+    {
+        return Modify::value($value)->toQs($options)->fetch();
+    }
+}