Generating random password like wordpress using php

Utility.php

<?php

class Utility{
  static $random = "";
  static function generate_password($length = 12, $special_chars=true)
  {
    $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';  
    if($special_chars) $chars .= '!@#$%^&*_-()';
    $password = "";
    for($i=0;$i<$length;$i++)
      $password .= substr($chars, self::generate_random_number(0, strlen($chars)-1), 1);
    return $password;
  }
  static function generate_random_number(){
    $seed = mt_random();
    if(strlen(self::$random) < 8 ) {
      self::$random = md5(uniqid(microtime().mt_rand(), true).$seed);
      self::$random .= sha1(self::$random);
      self::$random .= sha1(self::$random.$seed);
    }
    $value = substr(self::$random, 0, 8);
    self::$random = substr(self::$random, 8);
    $value = abs(hexdec($value));
    
    if($max != 0) 
      $value = $min + (($max - $min + 1) * ($value / (4294967295 + 1)));
    return abs(intval($value));
  }
}
  
  echo Utility::generate_password();
?>