Ez ok:
function PasswdGen($lenth) {
    // makes a random alpha numeric string of a given lenth
    $aZ09 = array_merge(range('A', 'Z'), range('a', 'z'),range(0, 9));
    $out ='';
    for($c=0;$c < $lenth;$c++) {
       $out .= $aZ09[mt_rand(0,count($aZ09)-1)];
    }
    return $out;
}

Ez Több helyen is X@rul működik:

function PasswdGen_2($chcount){
    $totalChar = $chcount;
    $salt = "1234567890qwertzuiopasdfghjklyxcvbnmQWERTZUIOPASDFGHJKLYXCVBNM";
    srand((double)microtime()*1000000);
    $user_passwd="";
    for($i=0;$i<$totalChar;$i++){
        $user_passwd=$user_passwd . substr($salt,rand()%strlen($salt),1);
    }
    return $user_passwd;
}