PHP function generate password

function genpass ($length=6){
 $password = "";  $possible = "0123456789bcdfghjkmnpqrstvwxyzQWERTYUIOPASDFGHJKLZXCVBNM";
 $i = 0; while ($i < $length) {
  $char = substr($possible, mt_rand(0, strlen($possible)-1), 1);
  if (!strstr($password, $char)) { $password .= $char;$i++;}
 }
 return $password;
}