php 也发一个生成随机字符串函数

/**
 * 生成随机数
 *
 * @param int $length 生成字符串长度
 * @param int $type 字符串类型
 * @param bool $special 是否使用特殊字符
 * @return string 返回生成的随机字符串
 * @example random(10, null, true);
 */
function random($length, $type = NULL, $special = FALSE) {
    $str = "";
    switch ($type) {
        case 1:
            $str = "0123456789";
            break;
        case 2:
            $str = "abcdefghijklmnopqrstuvwxyz";
            break;
        case 3:
            $str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            break;
        case 4:
            $str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            break;
        default:
            $str = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789";
        break;
    }
    return substr(str_shuffle(($special != FALSE) ? '!@#$%^&*()_+' . $str : $str), 0, $length);
}
//该片段来自于http://outofmemory.cn