PHP implementation of micro-blog Short link algorithm

Ideas:

1) will be long Web site MD5 generated 32-bit signature string, divided into 4 paragraphs, 8 bytes per paragraph;

2 to the four-segment loop, take 8 bytes, consider him as 16-string and 0X3FFFFFFF (30-bit 1) and operation, that is, more than 30-bit ignore processing;

3 The 30 bits are divided into 6 segments, each 5 digit number is taken as the index of the alphabet to obtain the specific characters, and then the 6-bit string is obtained.

4 The total MD5 string can obtain 4 6-bit string, and any one inside can be used as the short URL of this long URL;

Here is the PHP code:

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 = 0x3F FFFFFF & (1 * (' 0x '. $subHex));
      
   $out = ';
      
   for ($j = 0; $j < 6; $j + +) {
      
   $val = 0x0000001f & $int;
      
   $out. = $base 32[$val];
      
   $int = $int "5;
      
   }
      
   $output [] = $out;
      
   }
      
   return $output;
      
   }
      
   $urls = Shorturl (' http://www.bianceng.cn ');
      
   var_dump ($urls);