<?php
//短網(wǎng)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(jié)，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(shù)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(zhuǎn)為10進制數(shù)值型，否則運算會不正常
      $hex = hexdec($urlhash_piece) & 0x3fffffff;
 
      //域名根據(jù)需求填寫
      $short_url = "http://t.cn/";
      
      //生成6位短網(wǎng)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(huán)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);
?>