Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 18444)
+++ wp-includes/functions.php	(working copy)
@@ -256,7 +256,7 @@
 		return false;
 	if ( ':' !== $data[1] )
 		return false;
-	$lastc = $data[$length-1];
+	$lastc = substr($data, -1);
 	if ( ';' !== $lastc && '}' !== $lastc )
 		return false;
 	$token = $data[0];