AnsPress_Category::ap_question_form_fields( $form )

	public static function ap_question_form_fields( $form ) {
		if ( wp_count_terms( 'question_category' ) == 0 ) { // WPCS: loose comparison okay.
			return $form;
		}

		$editing_id = ap_sanitize_unslash( 'id', 'r' );

		$form['fields']['category'] = array(
			'label'    => __( 'Category', 'anspress-question-answer' ),
			'desc' 		 => __( 'Select a topic that best fits your question.', 'anspress-question-answer' ),
			'type'     => 'select',
			'options'  => 'terms',
			'order'    => 2,
			'validate' => 'required,not_zero',
		);

		// Add value when editing post.
		if ( ! empty( $editing_id ) ) {
			$categories = get_the_terms( $editing_id, 'question_category' );

			if ( $categories ) {
				$form['fields']['category']['value'] = $categories[0]->term_id;
			}
		}

		return $form;
	}