mt_rand_base62

<?php

    /**
     * 生成一个 $l 位的 62 进制随机字符串, 其第一位字符不为数字
     * @author Luyu Zhang<goocarlos@gmail.com>
     */
    function mt_rand_base62($l) {
      $c = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
      $letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
      for ($s = '', $cl = strlen($c)-1, $i = 0; $i < $l; $s .= $c[mt_rand(0, $cl)], ++$i);
      $s[0] = is_numeric($s[0])?$letters[mt_rand(0, strlen($letters)-1)]:$s[0];
      return $s;
    }