Cache API: Include the `cache-compat` file.

This was missed during the prior commit.

See [47938].



git-svn-id: https://develop.svn.wordpress.org/trunk@47939 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/cache-compat.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * Object Cache API functions missing from 3rd party object caches.
+ *
+ * @link https://codex.wordpress.org/Class_Reference/WP_Object_Cache
+ *
+ * @package WordPress
+ * @subpackage Cache
+ */
+
+if ( ! function_exists( 'wp_cache_get_multiple' ) ) :
+	/**
+	 * Compat function to mimic wp_cache_get_multiple.
+	 * Retrieves multiple values from the cache.
+	 *
+	 * @ignore
+	 * @since 5.5.0
+	 *
+	 * @see wp_cache_get_multiple()
+	 *
+	 * @param array $keys        Array of keys to fetch.
+	 * @param bool  $force       Optional. Unused. Whether to force a refetch rather than relying on the local
+	 *                           cache. Default false.
+	 *
+	 * @return array Array of values organized into groups.
+	 */
+	function wp_cache_get_multiple( $keys, $group = 'default', $force = false ) {
+		$values = array();
+
+		foreach ( $keys as $key ) {
+			$values[ $key ] = wp_cache_get( $key, $group, $force );
+		}
+
+		return $values;
+	}
+endif;