diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/Requests/src/Utility/CaseInsensitiveDictionary.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/Requests/src/Utility/CaseInsensitiveDictionary.php	Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,127 @@
+<?php
+/**
+ * Case-insensitive dictionary, suitable for HTTP headers
+ *
+ * @package Requests\Utilities
+ */
+
+namespace WpOrg\Requests\Utility;
+
+use ArrayAccess;
+use ArrayIterator;
+use IteratorAggregate;
+use ReturnTypeWillChange;
+use WpOrg\Requests\Exception;
+
+/**
+ * Case-insensitive dictionary, suitable for HTTP headers
+ *
+ * @package Requests\Utilities
+ */
+class CaseInsensitiveDictionary implements ArrayAccess, IteratorAggregate {
+	/**
+	 * Actual item data
+	 *
+	 * @var array
+	 */
+	protected $data = [];
+
+	/**
+	 * Creates a case insensitive dictionary.
+	 *
+	 * @param array $data Dictionary/map to convert to case-insensitive
+	 */
+	public function __construct(array $data = []) {
+		foreach ($data as $offset => $value) {
+			$this->offsetSet($offset, $value);
+		}
+	}
+
+	/**
+	 * Check if the given item exists
+	 *
+	 * @param string $offset Item key
+	 * @return boolean Does the item exist?
+	 */
+	#[ReturnTypeWillChange]
+	public function offsetExists($offset) {
+		if (is_string($offset)) {
+			$offset = strtolower($offset);
+		}
+
+		return isset($this->data[$offset]);
+	}
+
+	/**
+	 * Get the value for the item
+	 *
+	 * @param string $offset Item key
+	 * @return string|null Item value (null if the item key doesn't exist)
+	 */
+	#[ReturnTypeWillChange]
+	public function offsetGet($offset) {
+		if (is_string($offset)) {
+			$offset = strtolower($offset);
+		}
+
+		if (!isset($this->data[$offset])) {
+			return null;
+		}
+
+		return $this->data[$offset];
+	}
+
+	/**
+	 * Set the given item
+	 *
+	 * @param string $offset Item name
+	 * @param string $value Item value
+	 *
+	 * @throws \WpOrg\Requests\Exception On attempting to use dictionary as list (`invalidset`)
+	 */
+	#[ReturnTypeWillChange]
+	public function offsetSet($offset, $value) {
+		if ($offset === null) {
+			throw new Exception('Object is a dictionary, not a list', 'invalidset');
+		}
+
+		if (is_string($offset)) {
+			$offset = strtolower($offset);
+		}
+
+		$this->data[$offset] = $value;
+	}
+
+	/**
+	 * Unset the given header
+	 *
+	 * @param string $offset The key for the item to unset.
+	 */
+	#[ReturnTypeWillChange]
+	public function offsetUnset($offset) {
+		if (is_string($offset)) {
+			$offset = strtolower($offset);
+		}
+
+		unset($this->data[$offset]);
+	}
+
+	/**
+	 * Get an iterator for the data
+	 *
+	 * @return \ArrayIterator
+	 */
+	#[ReturnTypeWillChange]
+	public function getIterator() {
+		return new ArrayIterator($this->data);
+	}
+
+	/**
+	 * Get the headers as an array
+	 *
+	 * @return array Header data
+	 */
+	public function getAll() {
+		return $this->data;
+	}
+}