WP_REST_Posts_Controller::prepare_tax_query() WordPress Method

	private function prepare_tax_query( array $args, WP_REST_Request $request ) {
		$relation = $request['tax_relation'];

		if ( $relation ) {
			$args['tax_query'] = array( 'relation' => $relation );
		}

		$taxonomies = wp_list_filter(
			get_object_taxonomies( $this->post_type, 'objects' ),
			array( 'show_in_rest' => true )
		);

		foreach ( $taxonomies as $taxonomy ) {
			$base = ! empty( $taxonomy->rest_base ) ? $taxonomy->rest_base : $taxonomy->name;

			$tax_include = $request[ $base ];
			$tax_exclude = $request[ $base . '_exclude' ];

			if ( $tax_include ) {
				$terms            = array();
				$include_children = false;
				$operator         = 'IN';

				if ( rest_is_array( $tax_include ) ) {
					$terms = $tax_include;
				} elseif ( rest_is_object( $tax_include ) ) {
					$terms            = empty( $tax_include['terms'] ) ? array() : $tax_include['terms'];
					$include_children = ! empty( $tax_include['include_children'] );

					if ( isset( $tax_include['operator'] ) && 'AND' === $tax_include['operator'] ) {
						$operator = 'AND';
					}
				}

				if ( $terms ) {
					$args['tax_query'][] = array(
						'taxonomy'         => $taxonomy->name,
						'field'            => 'term_id',
						'terms'            => $terms,
						'include_children' => $include_children,
						'operator'         => $operator,
					);
				}
			}

			if ( $tax_exclude ) {
				$terms            = array();
				$include_children = false;

				if ( rest_is_array( $tax_exclude ) ) {
					$terms = $tax_exclude;
				} elseif ( rest_is_object( $tax_exclude ) ) {
					$terms            = empty( $tax_exclude['terms'] ) ? array() : $tax_exclude['terms'];
					$include_children = ! empty( $tax_exclude['include_children'] );
				}

				if ( $terms ) {
					$args['tax_query'][] = array(
						'taxonomy'         => $taxonomy->name,
						'field'            => 'term_id',
						'terms'            => $terms,
						'include_children' => $include_children,
						'operator'         => 'NOT IN',
					);
				}
			}
		}

		return $args;
	}