diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/Requests/Response/Headers.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/Requests/Response/Headers.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,98 @@
+<?php
+/**
+ * Case-insensitive dictionary, suitable for HTTP headers
+ *
+ * @package Requests
+ */
+
+/**
+ * Case-insensitive dictionary, suitable for HTTP headers
+ *
+ * @package Requests
+ */
+class Requests_Response_Headers extends Requests_Utility_CaseInsensitiveDictionary {
+	/**
+	 * Get the given header
+	 *
+	 * Unlike {@see self::getValues()}, this returns a string. If there are
+	 * multiple values, it concatenates them with a comma as per RFC2616.
+	 *
+	 * Avoid using this where commas may be used unquoted in values, such as
+	 * Set-Cookie headers.
+	 *
+	 * @param string $key
+	 * @return string Header value
+	 */
+	public function offsetGet($key) {
+		$key = strtolower($key);
+		if (!isset($this->data[$key])) {
+			return null;
+		}
+
+		return $this->flatten($this->data[$key]);
+	}
+
+	/**
+	 * Set the given item
+	 *
+	 * @throws Requests_Exception On attempting to use dictionary as list (`invalidset`)
+	 *
+	 * @param string $key Item name
+	 * @param string $value Item value
+	 */
+	public function offsetSet($key, $value) {
+		if ($key === null) {
+			throw new Requests_Exception('Object is a dictionary, not a list', 'invalidset');
+		}
+
+		$key = strtolower($key);
+
+		if (!isset($this->data[$key])) {
+			$this->data[$key] = array();
+		}
+
+		$this->data[$key][] = $value;
+	}
+
+	/**
+	 * Get all values for a given header
+	 *
+	 * @param string $key
+	 * @return array Header values
+	 */
+	public function getValues($key) {
+		$key = strtolower($key);
+		if (!isset($this->data[$key])) {
+			return null;
+		}
+
+		return $this->data[$key];
+	}
+
+	/**
+	 * Flattens a value into a string
+	 *
+	 * Converts an array into a string by imploding values with a comma, as per
+	 * RFC2616's rules for folding headers.
+	 *
+	 * @param string|array $value Value to flatten
+	 * @return string Flattened value
+	 */
+	public function flatten($value) {
+		if (is_array($value)) {
+			$value = implode(',', $value);
+		}
+
+		return $value;
+	}
+
+	/**
+	 * Get an iterator for the data
+	 *
+	 * Converts the internal
+	 * @return ArrayIterator
+	 */
+	public function getIterator() {
+		return new Requests_Utility_FilteredIterator($this->data, array($this, 'flatten'));
+	}
+}