用PHP实现URL转换短网址的算法示例

//短网址生成算法
class ShortUrl {
   
    //字符表
    public static $charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
 
    public static function encode($url)
    {
        $key = 'abc'; //加盐
        $urlhash = md5($key . $url);
        $len = strlen($urlhash);
 
        //将加密后的串分成4段，每段4字节，对每段进行计算，一共可以生成四组短连接
        for ($i = 0; $i < 4; $i++) {
            $urlhash_piece = substr($urlhash, $i * $len / 4, $len / 4);
           
            //将分段的位与0x3fffffff做位与，0x3fffffff表示二进制数的30个1，即30位以后的加密串都归零
            //此处需要用到hexdec()将16进制字符串转为10进制数值型，否则运算会不正常
            $hex = hexdec($urlhash_piece) & 0x3fffffff;
 
            //域名根据需求填写
            $short_url = "http://t.cn/";
           
            //生成6位短网址
            for ($j = 0; $j < 6; $j++) {
               
                //将得到的值与0x0000003d,3d为61，即charset的坐标最大值
                $short_url .= self::$charset[$hex & 0x0000003d];
               
                //循环完以后将hex右移5位
                $hex = $hex >> 5;
            }
 
            $short_url_list[] = $short_url;
        }
 
        return $short_url_list;
    }
}
 
$url = "http://www.111com.net/";
$short = ShortUrl::encode($url);
print_r($short);
?>