Custom search/filter form without views

Hello,

I have a very complex query which doesn't seem possible to do using views, so I've had to make my own version of it. Now I want to allow users to search and filter using my custom form and I want to know the right way to do this. The only way I've been able to make it work so far is having a page which checks post variables for anything posted back, pops it into the query which retrieves the content if there is anything, and then renders the form:

The menu item:

function workflow_menu() {
  $items = array();
  $items['admin/content/workflow/mycontent'] = array(
    'title' => 'My content',
    'file' => 'pages/workflow_mycontent.pages.inc',
    'page callback' => 'workflow_mycontent_display',
    'type' => MENU_LOCAL_TASK,
    'weight' => -9,
    'access arguments' => array('access workflow'),
  );
  return: items;
}

The display page:

/** 
 * Display and theme the content retrieved
 */
function workflow_mycontent_display() {
	// Get all of the user's content
	if(isset($_POST['content_type'])) {
		if(isset($_POST['content_title']))
			$mycontent = _workflow_get_mycontent($_POST['content_type'], $_POST['content_title']);
		else
			$mycontent = _workflow_get_mycontent($_POST['content_type']);
	}
	else
		$mycontent = _workflow_get_mycontent();	
	if(empty($mycontent)) 
		return '<p class="defaultnotavailable">You do not have any content</p>';
		
	$content = drupal_get_form('workflow_mycontent_form');
	$content .= '<div id="mycontent-wrapper">' . $mycontent . '</div>';
	return $content;
}

The form:

/**
 * Form for filtering content 
 */
function workflow_mycontent_form(&$form_state){
	$contenttypes = _workflow_get_content_types();
	$contenttypeoptions['all'] = 'All';
	foreach($contenttypes as $contenttype) {
		$contenttypeoptions[$contenttype] = str_replace('_', ' ', $contenttype);
	}

	$default = isset($form_state['post']['content_type']) ? $form_state['post']['content_type'] : 'all';
	$form['content_type'] = array(
		'#type' => 'select',
		'#title' => 'Filter by content type',
		'#default_value' => $default,
		'#options' =>  $contenttypeoptions,
		'#description' => 'Filter by content type',
		'#tree' => true,
	);
	$form['submit'] = array(
    '#type' => 'submit',
    '#value' => 'Filter',
  );
	$form['redirect'] = null;
	
	// There must be a better way...
	$_POST = array();
	return $form;
}

The query:

/**
 * Query the database to get current user's tasks in table form
 * Retrieves all pages, images, documents, news articles, links, events, garden events 
 * which currently have a value in the workflow taxonomy AND have a user reference to the current user 
 */
function _workflow_get_mycontent($type = null, $placeholders = null) {
  // Post variables
  $contenttypes = _workflow_get_content_types();
  if (isset($type) && in_array($type, $contenttypes))
    $contenttypessql = _workflow_get_content_types('sql', array($type));
  else
    $contenttypessql = _workflow_get_content_types('sql');
	
  // Build query to retrieve all tasks. 
  ............ lots of complex query stuff
  return theme_table($header, $mycontent, array('id' => 'mycontent', 'class' => 'workflow')); 
}

I'm pretty sure this is the "wrong" way to do it because in the documentation and on the forums people repeatedly say do not use post variables, plus I end up having to clear them at the bottom of the form function but I just CANNOT find another way to make this work. Can anybody tell me a better way to do this?

(And no, using form_state as a parameter in the form function to catch the post vars and then put them into the query results do not work, the form always submits twice, once with the correct variables and once without)

Thanks,
Rukaya