如何在PHP中将查询字符串转换为较短的字母数字字符串（然后再次转换回）？

Question

I want to store the query string of the current URL as a shorter alphanumeric string with the ability to convert it back to the original query string.

For example: inputType=timeline&count=50&hashtag=%23li&filterspecifiedhashtag=1&filterhashtagsend=1&filterscreennames=1&extracturl=1&deshortifyurl=1&filterurls=1

I want to be able to use the resultant alphanumeric string as a filename.

I want to avoid using MYSQL or storing values in a text file.

Is there a way to convert to an alphanumeric string as well as being able to convert it back to the original query string? I am not very knowledgeable about hashing but wondering whether some kind of "two way hashing" technique could work?

Answer 1

You can use base64_encode() and base64_decode(), but if you want it as a filename, you'll likely hit filename length limit of filesystem (255 chars for ext3). If it's possible you hit this limit, you can use each X chars as directory name, and create full path.

Answer 2

What you are seeking is not a hash - since hash is a one-way function in common case. Here is a possible solution - use both base64 encryption and something like parameters map, so you will able to get shorter file name because you'll not store parameters names, only values:

class Holder
{
   const NAME_PARAM_DELIMIER = '|';

   public static function getParametersMap()
   {
      return [
        0 => 'count',
        1 => 'deshortifyurl',
        2 => 'extracturl',
        3 => 'filterhashtagsend',
        4 => 'filterscreennames',
        5 => 'filterspecifiedhashtag',
        6 => 'filterurls',
        7 => 'hashtag',
        8 => 'inputType',
      ];
   }

   public static function getParamsByName($sName, $bReturnAsArray=true)
   {
      $rgParams = @array_combine(self::getParametersMap(), explode(self::NAME_PARAM_DELIMIER, base64_decode($sName)));
      if(!is_array($rgParams))
      {
         return null;
      }
      return $bReturnAsArray?$rgParams:http_build_query($rgParams);
   }

   public static function getNameByParams($sQuery)
   {
      parse_str($sQuery, $rgParams);
      ksort($rgParams);
      return base64_encode(join(self::NAME_PARAM_DELIMIER, array_values($rgParams)));
   }
}
$sQuery = 'inputType=timeline&count=50&hashtag=%23li&filterspecifiedhashtag=1&filterhashtagsend=1&filterscreennames=1&extracturl=1&deshortifyurl=1&filterurls=1';

$sName  = Holder::getNameByParams($sQuery);
$rgData = Holder::getParamsByName($sName);
var_dump($sName); //NTB8MXwxfDF8MXwxfDF8I2xpfHRpbWVsaW5l
var_dump($rgData);

Also note that base64 will produce "=" symbols - I am not sure that it is allowed on all file systems (I'm using Reiser, so it's ok in my case)