Description:
------------
Add an option in the php.ini file to make PHP read the first variable with the same key in the url. Thank you.

// --------------------------------
//
//
// PS.: Yes, it's possible to parse $_SERVER['QUERY_STRING'], but it would better to have a native option.
//
// PS².: Sorry if this is not the place for suggestions. 
//

Test script:
---------------
// Example URL: http://example.com/?var=foo&var=bar

ini_set('variables_key_order', 'first');

echo $_GET['var']; // => foo

// --------------------------------

ini_set('variables_key_order', 'last'); // last is default

echo $_GET['var']; // => bar