PHP Decode

<?php 
  function randomString($length, $type = '') { 
  // Select which type of characters you want in your random string 
  switch($type) { 
    case 'num': 
      // Use only numbers 
      $salt = '1234567890'; 
      break; 
    case 'lower': 
      // Use only lowercase letters 
      $salt = 'abcdefghijklmnopqrstuvwxyz'; 
      break; 
    case 'upper': 
      // Use only uppercase letters 
      $salt = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; 
      break; 
    default: 
      // Use uppercase, lowercase, numbers, and symbols 
      $salt = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'; 
      break; 
  } 
  $rand = ''; 
  $i = 0; 
  while ($i < $length) { // Loop until you have met the length 
    $num = rand() % strlen($salt); 
    $tmp = substr($salt, $num, 1); 
    $rand = $rand . $tmp; 
    $i++; 
  } 
  return $rand; // Return the random string 
} 
?>