新浪微博的mid转换成base62格式的PHP函数

最近有用到将新浪微博的mid地址转换成短格式编码的方法，例如：

221110410216147026

转换后：

zF4mOFpN7A

比如新浪微博地址可以组装成这样：​​http://weibo.com/1642634100/5en0UftjV8H​​，其中数字是用户的id，后面的字符串是base62加密后的mid，因此通过组装这两个，可以得到信息的主体。

本文的代码，是由​​http://forum.open.weibo.com/read.php?tid=3236&uid=89934​​的博主的js代码改成php而来

贴下代码，运行和博主的一样，这里只是将mid转成短格式，其实逆向也很好改了：

<?php
$str62keys = array (
"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" , "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"
) ;
 
/**
* 10进制值转换为62进制
* @param {String} int10 10进制值
* @return {String} 62进制值
*/
function int10to62 ( $int10 ) {
     global $str62keys ;
     $s62 = '' ;
     $r = 0 ;
     while ( $int10 != 0 )
     {
         $r = $int10 % 62 ;
         $s62 = $str62keys [ $r ] . $s62 ;
         $int10 = floor ( $int10 / 62 ) ;
     }
     return $s62 ;
}
/**
*
* 通过mid获得短格式
* @param string $mid
* @return 短格式
*/
function getCodeByMid ( $mid ) {
     $url = '' ;
    
     for ( $i = strlen ( $mid ) - 7 ; $i > - 7 ; $i -= 7 )      //从最后往前以7字节为一组读取mid
     {
         $offset1 = $i < 0 ? 0 : $i ;
         $offset2 = $i + 7 ;
         $num = substr ( $mid , $offset1 , $offset2 - $offset1 ) ;
         //mid.substring(offset1, offset2);
        
         $num = int10to62 ( $num ) ;
         $url = $num . $url ;
     }
    
     return $url ;
}
 
echo getCodeByMid ( '221110410216147026' ) ;
?>

为了方便，这里把那位博主的js代码也贴在这里，大家可以做一个对照：

/**
* 新浪微博mid与url互转实用工具
* 作者: XiNGRZ (http://weibo.com/xingrz)
*/
 
var WeiboUtility = { } ;
 
/**
* 62进制字典
*/
WeiboUtility . str62keys = [
     "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" ,
     "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"
] ;
 
/**
* 62进制值转换为10进制
* @param {String} str62 62进制值
* @return {String} 10进制值
*/
WeiboUtility . str62to10 = function ( str62 ) {
     var i10 = 0 ;
     for ( var i = 0 ; i < str62 . length ; i ++ )
     {
         var n = str62 . length - i - 1 ;
         var s = str62 [ i ] ;
         i10 += this . str62keys . indexOf ( s ) * Math . pow ( 62 , n ) ;
     }
     return i10 ;
} ;
 
/**
* 10进制值转换为62进制
* @param {String} int10 10进制值
* @return {String} 62进制值
*/
WeiboUtility . int10to62 = function ( int10 ) {
     var s62 = '' ;
     var r = 0 ;
     while ( int10 != 0 )
     {
         r = int10 % 62 ;
         s62 = this . str62keys [ r ] + s62 ;
         int10 = Math . floor ( int10 / 62 ) ;
     }
     return s62 ;
} ;
 
/**
* URL字符转换为mid
* @param {String} url 微博URL字符，如 "wr4mOFqpbO"
* @return {String} 微博mid，如 "201110410216293360"
*/
WeiboUtility . url2mid = function ( url ) {
     var mid = '' ;
    
     for ( var i = url . length - 4 ; i > - 4 ; i = i - 4 )      //从最后往前以4字节为一组读取URL字符
     {
         var offset1 = i < 0 ? 0 : i ;
         var offset2 = i + 4 ;
         var str = url . substring ( offset1 , offset2 ) ;
        
         str = this . str62to10 ( str ) ;
         if ( offset1 > 0 )      //若不是第一组，则不足7位补0
         {
             while ( str . length < 7 )
             {
                 str = '0' + str ;
             }
         }
        
         mid = str + mid ;
     }
    
     return mid ;
} ;
 
/**
* mid转换为URL字符
* @param {String} mid 微博mid，如 "201110410216293360"
* @return {String} 微博URL字符，如 "wr4mOFqpbO"
*/
WeiboUtility . mid2url = function ( mid ) {
     if ( typeof ( mid ) != 'string' ) return false ;      //mid数值较大，必须为字符串！
    
     var url = '' ;
    
     for ( var i = mid . length - 7 ; i > - 7 ; i = i - 7 )      //从最后往前以7字节为一组读取mid
     {
         var offset1 = i < 0 ? 0 : i ;
         var offset2 = i + 7 ;
         var num = mid . substring ( offset1 , offset2 ) ;
        
         num = this . int10to62 ( num ) ;
         url = num + url ;
     }
    
     return url ;
} ;