PHPでランダムなパスワードを生成する方法

function random_readable_pwd($length=10){
  // the wordlist from which the password gets generated 
  // (change them as you like)
  $words = 'dog,cat,sheep,sun,sky,red,ball,happy,ice,';
  $words .= 'green,blue,music,movies,radio,green,turbo,';
  $words .= 'mouse,computer,paper,water,fire,storm,chicken,';
  $words .= 'boot,freedom,white,nice,player,small,eyes,';
  $words .= 'path,kid,box,black,flower,ping,pong,smile,';
  $words .= 'coffee,colors,rainbow,plus,king,tv,ring';
  // Split by ",":
  $words = explode(',', $words);
  if (count($words) == 0){ die('Wordlist is empty!'); }
  // Add words while password is smaller than the given length
  $pwd = '';
  while (strlen($pwd) < $length){
    $r = mt_rand(0, count($words)-1);
    $pwd .= $words[$r];
  }
  // append a number at the end if length > 2 and
  // reduce the password size to $length
  $num = mt_rand(1, 99);
  if ($length > 2){
    $pwd = substr($pwd,0,$length-strlen($num)).$num;
  } else { 
    $pwd = substr($pwd, 0, $length);
  }
  return $pwd;
}
//使用范例：
random_readable_pwd(10) => returns something like: pingwater6, radiohap28, sunwhite84, happykid44, etc...