Contributing to PHP functions list

I always look for a function in php like this... maybe it help other //Insere uma string na posição desejada Inserts a string at desired position function ins_str($str,$chr,$pos){ if ($pos > 0){ $str = substr($str,0,$pos).$chr.substr($str,$pos); }elseif($pos < 0){ $str = substr($str,0,$pos).$chr.substr($str,$pos); }else{ $str = $str; } return $str; } ins_str("99999999","-",3) // Shows 999-99999 ins_str("99999999"," ",-4)//Shows 9999 9999 can help in simple masks