if statement in wp_query arguments

Question

I use $_POST form to get multiple elements from a form. The main problem is when I have multiple "if statements". It can become a true mess with nested statements when I want to check if multiple strings exist...

$cat = // Categories

if(!empty($cat)) {
   $args = array(  
    'post_type' => 'domains',
    'post_status' => 'publish',
      'tax_query' => array(
          array (
              'taxonomy' => 'domain_categories', 
              'field' => 'slug',
              'terms' => $cat, // ELEMENT EXISTS FOR $cat
          ),
      ), 
); 
} else { // ELSE STATEMENT IF $cat DOESN'T EXIST
    $args = array(  
        'post_type' => 'domains',
        'post_status' => 'publish',
    );
} // END STATEMENT FOR $cat

So, I would like to be able to simplify this.

Answer 1

As said here : Conditional arguments for WP_Query and tax_query depending on if $somevar has a value

I can define the args outside of the WP_Query instantiation:

<?php
$tax_query = array('relation' => 'AND');
    if (isset($search_course_area))
    {
        $tax_query[] =  array(
                'taxonomy' => 'course-area',
                'field' => 'id',
                'terms' => $search_course_area
            );
    }
    if (isset($search_course_level))
    {
        $tax_query[] =  array(
                'taxonomy' => 'study-levels',
                'field' => 'id',
                'terms' => $search_course_level
            );
    }
    if (isset($search_course_mode))
    {
        $tax_query[] =  array(
                'taxonomy' => 'course-mode',
                'field' => 'id',
                'terms' => $search_course_mode
            );
    }

$query = new WP_Query(
    array(
        //Retreive ALL course posts
        'post_type' => 'course',
        'posts_per_page' => '-1',
        //Filter taxonomies by id's passed from course finder widget
        'tax_query' => $tax_query,
    )
);
?>