Include posts from some categories while excluding from others

Question

I cannot successfully filter posts from some categories and exclude at the same time from others. The code is working perfectly when used to include only posts from a given category. Categories to be included are subcategories and the excluded categories are main categories (they're not parents to the included subcategories)

Examples:

1) Use both category__in and category__not_in at the same time

$wpid = get_category_id($_REQUEST['param']);
$cat_arr  = array($wpid);
$args = array( 
   'category__in' =>   $cat_arr,
   'category__not_in' =>   array(350,351),                
   'posts_per_page' => 10,
   'post_status' => 'publish',
   'suppress_filters' => 0
);

$the_query = new WP_Query( $args );
while ($the_query -> have_posts()){
.
.
}

2) Use only category__in with negative values:

$wpid = get_category_id($_REQUEST['param']);
$cat_arr  = array($wpid);
array_push($cat_arr, -350, -351);
$args = array( 
   'category__in' =>   $cat_arr,              
   'posts_per_page' => 10,
   'post_status' => 'publish',
   'suppress_filters' => 0
);

$the_query = new WP_Query( $args );
while ($the_query -> have_posts()){
.
.
}

Answer 1

You could use a Taxonomy Query, like so:

$args = array(
    'tax_query' => array(
        'relation' => 'AND',
        array(
            'taxonomy' => 'category',
            'terms'    => array(),
            'operator' => 'IN'
        ),
        array(
            'taxonomy' => 'category',
            'terms'    => array(),
            'operator' => 'NOT IN',
        ),
    ),
);
$query = new WP_Query( $args );

This will query posts that are in the first set of terms AND not in the second set.

Answer 2

Try this code. Not tested though

<?php

$args = array(
    'tax_query' => array(
        'relation' => 'AND', // logical relationship between taxonomy arrays
        array( // subcategories to exclude
            'taxonomy'      => 'category',
            'field'         => 'term_id',
            'terms'         => array(350, 351),
            'operator'      => 'NOT IN', // exclude
            'post_parent'   => 0 // top level only
        ),
        array( // categories to include
            'taxonomy'      => 'category',
            'field'         => 'term_id',
            'terms'         => array($cat_arr),
            // 'include_children' => false
        )
    ),
    'posts_per_page' => 10,
    // more lines if needed
);

I omited suppress_filters because it is not appropriate with WP_Query.

May be you'll want to use 'include_children' => false (commented out in the code) if you don't want to show posts from $cat_arr subcategories.