-if (!function_exists('is_a')) {
- function is_a($object, $class) {
- // by Aidan Lister <aidan@php.net>
- if (get_class($object) == strtolower($class)) {
- return true;
- } else {
- return is_subclass_of($object, $class);
- }
+if ( !function_exists('mb_substr') ):
+ function mb_substr( $str, $start, $length=null, $encoding=null ) {
+ return _mb_substr($str, $start, $length, $encoding);
+ }
+endif;
+
+function _mb_substr( $str, $start, $length=null, $encoding=null ) {
+ // the solution below, works only for utf-8, so in case of a different
+ // charset, just use built-in substr
+ $charset = get_option( 'blog_charset' );
+ if ( !in_array( $charset, array('utf8', 'utf-8', 'UTF8', 'UTF-8') ) ) {
+ return is_null( $length )? substr( $str, $start ) : substr( $str, $start, $length);