类代码:

<?php
/**
 * PHP - Password Generator Class
 * Version 1.0.0
 *
 */
 
if (@!is_object($passGen) || !isset($passGen)) {
  $passGen = new Password;
}
 
class Password
{
 
  /**
   * 大写字母 A-Z
   *
   * @var array
   */
  protected $uppercase_chars;
 
  /**
   * 小写字母 a-z
   *
   * @var array
   */
  protected $lowercase_chars;
 
  /**
   * 阿拉伯数字 0-9
   *
   * @var array
   */
  protected $number_chars;
 
  /**
   * 特殊字符
   *
   * @var array
   */
  protected $special_chars;
 
  /**
   * 其他特殊字符
   *
   * @var array
   */
  protected $extra_chars;
 
  /**
   * 最终用来生成密码的所有字符
   *
   * @var array
   */
  protected $chars = array();
 
  /**
   * 密码长度
   *
   * @var array
   */
  public $length;
 
  /**
   * 是否使用大写字母
   *
   * @var boolean
   */
  public $uppercase;
 
  /**
   * 是否使用小写字母
   *
   * @var boolean
   */
  public $lowercase;
 
  /**
   * 是否使用阿拉伯数字
   *
   * @var boolean
   */
  public $number;
 
  /**
   * 是否使用特殊字符
   *
   * @var boolean
   */
  public $special;
 
  /**
   * 是否使用额外的特殊字符
   *
   * @var boolean
   */
  public $extra;
 
  /**
   * 初始化密码设置
   *
   * @param int $length
   */
  function Password($length = 12)
  {
    $this->length = $length;
     
    $this->configure(true, true, true, false, false);
  }
 
  /**
   * 配置
   */
  function configure($uppercase = false, $lowercase = false, $number = false,
            $special = false, $extra = false
  ) {
    $this->chars = array();
 
    $this->upper_chars  = array(
                 "A", "B", "C", "D", "E", "F", "G", "H", "I",
                 "J", "K", "L", "M", "N", "O", "P", "Q", "R",
                 "S", "T", "U", "V", "W", "X", "Y", "Z"
                );
    $this->lower_chars  = array(
                 "a", "b", "c", "d", "e", "f", "g", "h", "i",
                 "j", "k", "l", "m", "n", "o", "p", "q", "r", 
                 "s", "t", "u", "v", "w", "x", "y", "z"
                );
    $this->number_chars = array(
                 "1", "2", "3", "4", "5", "6", "7", "8", "9", "0"
                );
    $this->special_chars = array(
                 "!", "@", "#", "$", "%", "^", "&", "*", "(", ")"
                );
    $this->extra_chars  = array(
                 "[", "]", "{", "}", "-", "_", "+", "=", "<",
                 ">", "?", "/", "`", "~", "|", ",", ".", ";", ":"
                );
 
    if (($this->uppercase = $uppercase) === true) {
      $this->chars = array_merge($this->chars, $this->upper_chars);
    }
    if (($this->lowercase = $lowercase) === true) {
      $this->chars = array_merge($this->chars, $this->lower_chars);
    }
    if (($this->number = $number) === true) {
      $this->chars = array_merge($this->chars, $this->number_chars);
    }
    if (($this->special = $special) === true) {
      $this->chars = array_merge($this->chars, $this->special_chars);
    }
    if (($this->extra = $extra) === true) {
      $this->chars = array_merge($this->chars, $this->extra_chars);
    }
 
    $this->chars = array_unique($this->chars);
  }
   
  /**
   * 从字符列中生成随机密码
   *
   * @return string
   **/
  function generate()
  {
    if (empty($this->chars)) {
      return false;
    }
 
    $hash    = "";
    $totalChars = count($this->chars) - 1;
     
    for ($i = 0; $i < $this->length; $i++) {
      $hash .= $this->chars[$this->random(0, $totalChars)];
    }
 
    return $hash;
  }
 
  /**
   * 生成随机数字
   *
   * @return int
   */
  function random($min = 0, $max = 0)
  {
    $max_random = 4294967295;
 
    $random = uniqid(microtime() . mt_rand(), true);
    $random = sha1(md5($random));
 
    $value = substr($random, 0, 8);
    $value = abs(hexdec($value));
 
    if ($max != 0) {
      $value = $min + ($max - $min + 1) * $value / ($max_random + 1);
    }
 
    return abs(intval($value));
  }
}

调用:

<?php
 
include_once "password.class.php";
 
echo $passGen->generate();
 
//FS4yq74e2LeE