<?php    $array = array(
      "collection" => "departments",
      "action" => "find",
      "args" => array ("_id" => array('$in' => "{{variablename}}"))
    );
    $stack = array(&$array);
    while (sizeof($stack) > 0) {
        foreach ($stack as &$current) {
            break;
        }
        $stack = array_slice($stack, 1);
        if (is_array($current)) {
            foreach ($current as &$value) {
                $stack[] =& $value;
            }
        } elseif ($current == '{{variablename}}') {
            break;
        }
    }
    $current = 'test';
    var_dump($current);
    var_dump($array);