PHP function to obtain string length under UTF-8 and GBK encoding

/*
* Count string length
*@param $str Counted string
*/
function sstrlen($str) {
global $charset;
 $n = 0; $p = 0; $c = ”;
$len = strlen($str);
if($charset == 'utf-8′) {
for($i = 0; $i < ; $len; $i++) {
$c = ord($str{$i});
if($c > 252) {
$p = 5;
} elseif($c > 248) {
 $p = 4;
} elseif($c > 240) {
$p = 3;
} elseif($c > 224) {
$p = 2;
} elseif($c > 192) {
$p = 1;
} else {
$p = 0;
}
$i+=$p;$n++;
}
} else {
for($i = 0; $i < $len; $ i++) {
$c = ord($str{$i});
if($c > 127) {
$p = 1;
} else {
$p = 0;
}
$i+=$ p;$n++;
}
}
return $n;
}
?>