CCReddit PHP

<?php
  function randomPassword() {
    $alphabet = "abcdefghijklmnopqrstuwxyzABCDEFGHIJKLMNOPQRSTUWXYZ0123456789";
    $pass = array(); //remember to declare $pass as an array
    $alphaLength = strlen($alphabet) - 1; //put the length -1 in cache
    for ($i = 0; $i < 12; $i++) {
        $n = rand(0, $alphaLength);
        $pass[] = $alphabet[$n];
    }
    return implode($pass); //turn the array into a string
  }

  $pass = randomPassword();
  $file = fopen("pass.txt", "w") or die("Unable to open file!");
  fwrite($file, $pass);
  fclose($file);
  echo $pass;
?>