+
+/**
+ * Generate a random UUID (version 4).
+ *
+ * @since 4.7.0
+ *
+ * @return string UUID.
+ */
+function wp_generate_uuid4() {
+ return sprintf( '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+ mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ),
+ mt_rand( 0, 0xffff ),
+ mt_rand( 0, 0x0fff ) | 0x4000,
+ mt_rand( 0, 0x3fff ) | 0x8000,
+ mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff )
+ );
+}
+
+/**
+ * Get last changed date for the specified cache group.
+ *
+ * @since 4.7.0
+ *
+ * @param $group Where the cache contents are grouped.
+ *
+ * @return string $last_changed UNIX timestamp with microseconds representing when the group was last changed.
+ */
+function wp_cache_get_last_changed( $group ) {
+ $last_changed = wp_cache_get( 'last_changed', $group );
+
+ if ( ! $last_changed ) {
+ $last_changed = microtime();
+ wp_cache_set( 'last_changed', $last_changed, $group );
+ }
+
+ return $last_changed;
+}