PHP replace n string

function str_replace_count($search,$replace,$subject,$times) {
    $subject_original=$subject;
    $len=strlen($search);
    $pos=0;
    for ($i=1;$i<=$times;$i++) {
        $pos=strpos($subject,$search,$pos);
        if($pos!==false) {
            $subject=substr($subject_original,0,$pos);
            $subject.=$replace;
            $subject.=substr($subject_original,$pos+$len);
            $subject_original=$subject;
        } else {
            break;
        }
    }
    return($subject);
}
?>



To use it, just call the function, like this:
$myString = "X. Xavier Reynolds";
print str_replace_count("X","A",$myString,1);
?>