gistfile1.php

// Being sent from a form via AJAX that gets URI encoded
list[1]=root&list[68]=root&list[67]=root

// Data from $this->input->data
list%5B1%5D%3Droot%26list%5B68%5D%3Droot%26list%5B67

<?php
$parts = parse_url($this->input->post('data'));
$query = array();
parse_str($parts['path'], $query);
print_r($query);
?>

// Results
Array
(
    [list] => Array
        (
            [1] => 
        )

)