微博短链接算法php版本

思绪：
1)将长网址md5天生32位署名串,分为4段, 每段8个字节;
2)对这四段轮回处理赏罚, 取8个字节, 将他当作16进制串与0x3fffffff(30位1)与操纵, 即高出30位的忽略处理赏罚;
3)这30位分成6段, 每5位的数字作为字母表的索引取得特定字符, 依次举办得到6位字符串;
4)总的md5串可以得到4个6位串; 取内里的恣意一个就可作为这个长url的短url地点;

下面是PHP代码:

function shorturl($url='', $prefix='', $suffix='') {
    $base = array (
       'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
       'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
       'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
       'y', 'z', '0', '1', '2', '3', '4', '5');

    $hex = md5($prefix.$url.$suffix);
    $hexLen = strlen($hex);
    $subHexLen = $hexLen / 8;
    $output = array();

    for ($i = 0; $i < $subHexLen; $i++) {
        $subHex = substr ($hex, $i * 8, 8);
        $int = 0x3FFFFFFF & (1 * ('0x'.$subHex));
        $out = '';
        for ($j = 0; $j < 6; $j++) {
            $val = 0x0000001F & $int;
            $out .= $base[$val];
            $int = $int >> 5;
        }
        $output[] = $out;
    }
    return $output;
}

$urls = shorturl('http://www.hdj.me/');
var_dump($urls);

功效

array(4) {
  [0]=>
  string(6) "alms1l"
  [1]=>
  string(6) "2ipmby"
  [2]=>
  string(6) "avo1hu"
  [3]=>
  string(6) "fdlban"
}

其它一个版本：

function shorturl($url='', $prefix='', $suffix='') {
    $base = array(
            "a","b","c","d","e","f","g","h",
            "i","j","k","l","m","n","o","p",
            "q","r","s","t","u","v","w","x",
            "y","z","0","1","2","3","4","5",
            "6","7","8","9","A","B","C","D",
            "E","F","G","H","I","J","K","L",
            "M","N","O","P","Q","R","S","T",
            "U","V","W","X","Y","Z");
 
    $hex = md5($prefix.$url.$suffix);
    $hexLen = strlen($hex);
    $subHexLen = $hexLen / 8;
    $output = array();
 
    for ($i = 0; $i < $subHexLen; $i++) {
        $subHex = substr ($hex, $i * 8, 8);
        $int = 0x3FFFFFFF & (1 * ('0x'.$subHex));
        $out = '';
        for ($j = 0; $j < 6; $j++) {
            $val = 0x0000003D & $int;
            $out .= $base[$val];
            $int = $int >> 5;
        }
        $output[] = $out;
    }
    return $output;
}