Артем Золин

$background_image = get_the_post_thumbnail_url( get_the_ID(), 'full' );
echo '<section class="hero" style="background: url(' . $background_image . ') center no-repeat">';

$args = array( 
	'post_type' => 'product', 
	'posts_per_page' => 99,
	'order' => 'DESC', // Display all post with thumbnail ID first 
	'orderby' => 'meta_value_num', // order by meta key value
	'meta_query' => array(  //query post based on meta key
		array(
			'relation' => 'OR', // add condition if meta key is exists or not
			array(
				'key' => '_thumbnail_id', 
				'compare' => 'NOT EXISTS' // include post without _thumbnail_id key
			),
			array(
				'key' => '_thumbnail_id', 
				'compare' => '!NOT EXISTS' // include post with _thumbnail_id key
			)
		)
	)
);

$categories = get_terms();
foreach ( $categories as $key => $category ) {
	if ( $category->parent == 0 ) {
		# нет родителя
	} else {
		# есть родитель
	}
}

function is_category_parent( $cat_id ) {
	$category = get_category( $cat_id );
	if ( $category->parent == 0 ) {
		return true;
	}
	return false;
}

if ( is_category_parent( $cat_id ) ) {
	// категория имеет родителя
}

<?php get_header(); ?>

	<div id="primary" class="content-area">
		<main id="main" class="site-main" role="main">

		<?php if ( have_posts() ) : ?>

			<header class="page-header">
				<?php
					the_archive_title( '<h1 class="page-title">', '</h1>' );
					the_archive_description( '<div class="taxonomy-description">', '</div>' );
				?>
			</header><!-- .page-header -->

			<?php
			// Start the loop.
			while ( have_posts() ) :
				the_post();

				get_template_part( 'template-parts/content', get_post_format() );

				// End the loop.
			endwhile;

			// Previous/next page navigation.
			the_posts_pagination(
				array(
					'prev_text'          => __( 'Previous page', 'twentysixteen' ),
					'next_text'          => __( 'Next page', 'twentysixteen' ),
					'before_page_number' => '<span class="meta-nav screen-reader-text">' . __( 'Page', 'twentysixteen' ) . ' </span>',
				)
			);

			// If no content, include the "No posts found" template.
		else :
			get_template_part( 'template-parts/content', 'none' );

		endif; ?>

		</main><!-- .site-main -->
	</div><!-- .content-area -->

<?php get_sidebar(); ?>
<?php get_footer(); ?>

$queried_object = get_queried_object();

if ( is_tax( 'projects' ) && isset( $queried_object->term_id ) ) {

	$query = new WP_Query( [
		'post_type' => 'portfolio',
		'posts_per_page' => 10,
		'tax_query' => [
			[
				'taxonomy' => 'projects',
				'field'    => 'id',
				'terms'    => $queried_object->term_id,
			],
		]
	] );

}

$classes[] = 'project-item col-lg-4 col-md-6 col-sm-12';

$project_taxes = get_the_terms( $post->ID, 'project_tax' );
if( is_array( $project_taxes ) ) {
	foreach ( $project_taxes as $key => $project_tax ) {
		$classes[] = $project_tax->slug;
	}
}

echo '<div class="' . implode( ' ', $classes ) . '">';
	echo '<h2>' . $post->post_title . '</h2>';
echo '</div>';

add_filter( 'wp_mail_content_type', function( $content_type ) {
	return "text/html";
});

$headers = 'From: My Name <myname@mydomain.com>' . "\r\n";
$html = '<p>The <em>HTML</em> message</p>';

wp_mail( 'me@example.com', 'The subject', $html, $headers );

PHP-код, встроенный в страницу будет разбирать строку GET-запроса от API сервиса бронирования и, на основании данных из запроса, формировать сообщение о результате бронирования.

if ( $condition ) {
	get_template_part( 'templates/thankyou' );
} else {
	get_template_part( 'templates/common' );
}