How to push both value and key into PHP array

Take a look at this code:

$GET = array();    
$key = 'one=1';
$rule = explode('=', $key);
/* array_push($GET, $rule[0] => $rule[1]); */

I’m looking for something like this so that:

print_r($GET);
/* output: $GET[one => 1, two => 2, ...] */

Is there a function to do this? (because array_push won’t work this way)