php生成短网址原理与实例

例1，php生成短网址。

2. $chars=array("a","b","c","d","e","f","g","h",
3. "i","j","k","l","m","n","o","p",
4. "q","r","s","t","u","v","w","x",
5. "y","z","0","1","2","3","4","5",
6. "6","7","8","9","A","B","C","D",
7. "E","F","G","H","I","J","K","L",
8. "M","N","O","P","Q","R","S","T",
9. "U","V","W","X","Y","Z");
10. $salt="www.joneto.com";
11. $hash=md5("http://bbs.it-home.org".$salt);
12. $rs=array();
13. for($i=0;$i $temp=substr($hash, $i*8,8);
14. $temp=base_convert($temp, 16, 10) & base_convert("3fffffff", 16, 10);
15. $str="";
16. for($j=0;$j $subtemp=$temp & intval(base_convert("3d", 16, 10));
17. $str.=$chars[$subtemp];
18. $temp=$temp>>5;
19. }
20. unset($temp);
21. $rs[]=$str;
22. }
23. print_r($rs);
24. ?>

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php 生成短网址原理及代码

将原网址做crc32校验，得到校验码，使用sprintf将校验码转为无符号数字。

php 生成短网址 原理：

1.将原网址做crc32校验，得到校验码。

2.使用sprintf('%u') 将校验码转为无符号数字。

3.对无符号数字进行求余62操作（大小写字母+数字等于62位），得到余数后映射到62个字符中，将映射后的字符保存。（例如余数是10，则映射的字符是A，0-9对应0-9，10-35对应A-Z，35-62对应a-z）

4.循环操作，直到数值为0。

5.将所有映射后的字符拼接，就是短网址后的code。

3. /** 生成短网址

4. * @param String $url 原网址
5. * @return String
6. */
7. function dwz($url){

8. $code = sprintf('%u', crc32($url));

9. $surl = '';

10. while($code){

11. $mod = $code % 62;
12. if($mod>9 && $mod$mod = chr($mod + 55);
13. }elseif($mod>35){
14. $mod = chr($mod + 61);
15. }
16. $surl .= $mod;
17. $code = floor($code/62);
18. }
19. return $surl;
20. }

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