get_query_var doe’s not work with a form using method POST

I’m trying to use the following code to build a ‘recommend’ page, but when I click the send button (form using method POST), the get_query_var does not return the correct value.

function recommend_redirect() {
	if(intval(get_query_var('recommend')) == 1) {
		remove_all_filters('the_content');

		add_filter('the_content', 'recommend_content');
		add_filter('the_title', 'recommend_title');
		add_filter('comments_template', 'recommend_comments');
	}
}

How to solve this?
Thanks

========== EDIT ==============
Problem solved.
I had a input called “recommend” and it’s value was rewriting the URL “recommend” variable.