minor #24949 [HttpFoundation] fixed return type of method HeaderBag::get (AmsTaFFix)

This PR was merged into the 2.7 branch.

Discussion
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[HttpFoundation] fixed return type of method HeaderBag::get

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

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Commits
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6b608e8 [HttpFoundation] fixed return type of method HeaderBag::get

src/Symfony/Component/HttpFoundation/HeaderBag.php

@@ -101,11 +101,11 @@ class HeaderBag implements \IteratorAggregate, \Countable
     /**
      * Returns a header value by name.
      *
-     * @param string $key     The header name
-     * @param mixed  $default The default value
-     * @param bool   $first   Whether to return the first value or all header values
+     * @param string          $key     The header name
+     * @param string|string[] $default The default value
+     * @param bool            $first   Whether to return the first value or all header values
      *
-     * @return string|array The first header value if $first is true, an array of values otherwise
+     * @return string|string[] The first header value or default value if $first is true, an array of values otherwise
      */
     public function get($key, $default = null, $first = true)
     {
@@ -129,9 +129,9 @@ class HeaderBag implements \IteratorAggregate, \Countable
     /**
      * Sets a header by name.
      *
-     * @param string       $key     The key
-     * @param string|array $values  The value or an array of values
-     * @param bool         $replace Whether to replace the actual value or not (true by default)
+     * @param string          $key     The key
+     * @param string|string[] $values  The value or an array of values
+     * @param bool            $replace Whether to replace the actual value or not (true by default)
      */
     public function set($key, $values, $replace = true)
     {