<?php//短網址生成算法class ShortUrl {    //字符表  public static $charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";   public static function encode($url)  {    $key = 'abc'; //加鹽    $urlhash = md5($key . $url);    $len = strlen($urlhash);     //將加密后的串分成4段，每段4字節，對每段進行計算，一共可以生成四組短連接    for ($i = 0; $i < 4; $i++) {      $urlhash_piece = substr($urlhash, $i * $len / 4, $len / 4);            //將分段的位與0x3fffffff做位與，0x3fffffff表示二進制數的30個1，即30位以后的加密串都歸零      //此處需要用到hexdec()將16進制字符串轉為10進制數值型，否則運算會不正常      $hex = hexdec($urlhash_piece) & 0x3fffffff;       //域名根據需求填寫      $short_url = "http://t.cn/";            //生成6位短網址      for ($j = 0; $j < 6; $j++) {                //將得到的值與0x0000003d,3d為61，即charset的坐標最大值        $short_url .= self::$charset[$hex & 0x0000003d];                //循環完以后將hex右移5位        $hex = $hex >> 5;      }       $short_url_list[] = $short_url;    }     return $short_url_list;  }} $url = "http://www.sunbloger.com/";$short = ShortUrl::encode($url);print_r($short);?>