AnsPress_Email_Hooks::form_allowed_tags()

	public static function form_allowed_tags() {
		$active = ap_isset_post_value( 'template', 'new_question' );

		$tags = array(
			'site_name', 'site_url', 'site_description',
		);

		$type_tags = [];

		if ( in_array( $active, [ 'new_question', 'edit_question' ] ) ) {
			$type_tags = array(
				'asker', 'question_title', 'question_link', 'question_content', 'question_excerpt',
			);
		} elseif ( in_array( $active, [ 'new_answer', 'edit_answer' ] ) ) {
			$type_tags = array(
				'answerer', 'question_title', 'answer_link', 'answer_content', 'answer_excerpt',
			);
		} elseif ( 'select_answer' === $active ) {
			$type_tags = array(
				'selector', 'question_title', 'answer_link', 'answer_content', 'answer_excerpt',
			);
		} elseif ( 'new_comment' === $active ) {
			$type_tags = array(
				'commenter', 'question_title', 'comment_link', 'comment_content',
			);
		}

		$tags = array_merge( $tags, $type_tags );

		$html = '';
		foreach ( $tags as $tag ) {
			$html .= '<pre>{' . esc_html( $tag ) . '}</pre>';
		}

		return $html;
	}