URL Argument separator

http://pollinimini.net/blog/url-argument-separator

Quite so often a web developer starts thinking what’s wrong with the guys who make the rules of how Internet works. And if we dig a bit in the problem, we can many times see that the ‘non-sense’ is there not because the specs were flawed but because the popular implementations didn’t follow completely the spec.

The ‘non-sense’ I’ve been thinking about lately is why the hell we use the ampersand [&] to separate the arguments in a URL. My problem with using the & as separator is that in todays world of XML crazyness, the ampersand must be handled with care. It seems that the specs said that any character could be used after the initial query char mark [?] but the [#] which marks the start of the fragment. In the current specs for URI/URL syntaxis they recommend the semicolon [;]

So the decision to choose the ampersand as the defacto standard was taken by the guys who took the lead with the CGI scripts and the dynamic web content generation.

Since the specs recommend the use of the semicolon I thought “ok, no problem, I’ll just use it from now on” with a grin in my face. If you are thinking the same keep reading because it’s not that easy. My server-side language of choice right now is PHP, so I build up a simple test script to check out if the semicolon worked ok, but it didn’t. After consulting php.net for a bit more of information I found the solution, there are two ini directives which define the argument separators, one for input and the other for output (I guess this last one is used to manage the session id without cookies). arg_separator.input and arg_separator.output are the names of the directives. The first one takes a string as argument and every char in that string becomes an argument separator, the second one defines what will PHP use when building URLs as separator.

The bad news is that the default value is just the ampersand [&]. The good news is that both directives can be defined per directory, so we can put them in our .htaccess in our shared hosts. If you control the host just edit the php.ini file. Logically we can’t modify them with ini_set() because the URI is already processed when our script starts execution (see below for a solution to this).

php_value arg_separator.input "&;"
php_value arg_separator.output ";"Copy to clipboard

Note that I left both: the ampersand [&] and the semicolor [;] as valid argument separators, I’m far too used to the ampersand and I don’t want to expend my whole life debugging an application just because I forgot that I decided that the semicolon was a better suit :)

Even if we can’t use the ini_set() function to modify the PHP behaviour for this, we can still make use of a different argument separator by processing the $_GET and $_REQUEST arrays and splitting them by our preffererd argument separator. The following code snippet show do it but please don’t use it in production environments, it’s probably flawed!

// first join the PHP splitted arguments
$get = '';
foreach ($_GET as $k=>$v) {
          $get.= $k . '=' . $v . ';';
          // remove from the arrays, we'll add the correct ones later
          unset($_GET[$k]);
          unset($_REQUEST[$k]);
}

// split the query string using our desired char
$args = split(';', $get);
// process the query string and rebuild the _GET and _REQUEST array
foreach ($args as $arg) {
          // now separate the key from the value and assign them to the arrays
          list($k,$v) = explode('=', $arg);
          if (! empty($k)) {
              $_GET[ $k ] = $v;
              $_REQUEST[ $k ] = $v;
          }
}Copy to clipboard

Changing the argument separator does not only help out when working with XML based technologies but also to give your site URLs a geeky look ;)