Jquery Ajax – post huge string value

You will need to use a POST request:

$.ajax({
    url: '/script.php',
    type: 'POST',
    data: { value: 'some huge string here' },
    success: function(result) {
        alert('the request was successfully sent to the server');
    }
});

and in your server side script retrieve the value:

$_POST["value"]

Also you might need to increase the allowed request size. For example in your .htaccess file or in your php.ini you could set the post_max_size value:

#set max post size
php_value post_max_size 20M