Check if a post is under knowledge category

scratch_102.php

<?php


function yell_is_knowledge_post( $post_id ) {
	$categories = get_the_category( $post_id );
	if ( in_array( 'knowledge', wp_list_pluck( $categories, 'slug' ), true ) ) {
		return true;
	}

	$knowledge_cat = get_term_by( 'slug', 'knowledge', 'category' );
	if ( ! is_a( $knowledge_cat, 'WP_Term' ) ) {
		// Knpwledge category does not even exist
		return false;
	}

	$parent_categories_ids = array_map( 'absint', wp_list_pluck( $categories, 'parent' ) );
	if ( in_array( $knowledge_cat->term_id, $parent_categories_ids, true ) ) {
		// Current category is child of Knowledge term
		return true;
	}

	// Search children terms. This is the slowest method but it won't get here often
	$categories_ids = wp_list_pluck( $categories, 'term_id' );
	if ( is_a( $knowledge_cat, 'WP_Term' ) ) {
		$children_ids = get_term_children( $knowledge_cat->term_id, 'category' );
		if ( array_intersect( $categories_ids, $children_ids ) ) {
			// One of the Knowledge children categories is assigned to this post
			return true;
		}
	}

	return false;
}


function test_something() {
	$post_id = $this->factory()->post->create();
	$knowledge_term = $this->factory()->term->create( array( 'slug' => 'knowledge', 'taxonomy' => 'category' ) );
	$different_term = $this->factory()->term->create( array( 'slug' => 'different', 'taxonomy' => 'category' ) );
	$child_knowledge_term = $this->factory()->term->create( array( 'slug' => 'child-knowledge', 'parent' => $knowledge_term, 'taxonomy' => 'category' ) );
	$grandchild_knowledge_term = $this->factory()->term->create( array( 'slug' => 'child-knowledge', 'parent' => $child_knowledge_term, 'taxonomy' => 'category' ) );

	$this->assertFalse( yell_is_knowledge_post( $post_id ) );

	$this->wp_set_object_terms( $post_id, $knowledge_term, 'category' );
	$this->assertTrue( yell_is_knowledge_post( $post_id ) );

	$this->wp_set_object_terms( $post_id, $child_knowledge_term, 'category' );
	$this->assertTrue( yell_is_knowledge_post( $post_id ) );

	$this->wp_set_object_terms( $post_id, $different_term, 'category' );
	$this->assertFalse( yell_is_knowledge_post( $post_id ) );

	$this->wp_set_object_terms( $post_id, $grandchild_knowledge_term, 'category' );
	$this->assertTrue( yell_is_knowledge_post( $post_id ) );
}