Владимир Брумер

if ( ! function_exists( 'get_wpgen_header_classes' ) ) {

	/**
	 * Get classes for header container.
	 *
	 * @param string $class Additional header classes.
	 *
	 * @return array
	 */
	function get_wpgen_header_classes( $class = '' ) {

		// Add elements to array.
		$classes   = array();
		$classes[] = 'header';

		if ( has_custom_header() ) {
			$classes[] = 'header--background-image';
		}

		if ( is_front_page() || is_home() ) {
			$classes[] = 'header-bg';
		} else {
			$classes[] = 'custom-class';
		}

		// Check the function has accepted any classes.
		if ( isset( $class ) && ! empty( $class ) ) {
			if ( is_array( $class ) ) {
				$classes = array_merge( $classes, $class );
			} elseif ( is_string( $class ) ) {
				$classes = array_merge( $classes, explode( ' ', $class ) );
			}
		}

		$classes = apply_filters( 'get_wpgen_header_classes', $classes );

		// Usage:
		/*add_filter( 'get_wpgen_header_classes', 'my_header_classes' );
		if ( ! function_exists( 'my_header_classes' ) ) {
			function my_header_classes( $classes ) {
				$classes[] = 'my-class';
				return array_unique( $classes );
			}
		}*/

		return array_unique( (array) $classes );
	}
}

if ( ! function_exists( 'wpgen_header_classes' ) ) {

	/**
	 * Display classes for header container.
	 *
	 * @param string $class Additional header classes.
	 * @param bool   $echo  Echo or return header classes.
	 *
	 * @return string
	 */
	function wpgen_header_classes( $class = '', $echo = true ) {

		$classes = get_wpgen_header_classes( $class );

		if ( $echo ) {
			echo 'class="' . esc_attr( implode( ' ', $classes ) ) . '"';
		} else {
			return 'class="' . esc_attr( implode( ' ', $classes ) ) . '"';
		}
	}
}

<header id="header" <?php wpgen_header_classes(); ?>>

<header id="header" <?php wpgen_header_classes( 'new-class' ); ?>>

<form id="filter">
  <div class="search-holder">
    <input type="search" name="s" id="s" class="input-text" placeholder="<?php esc_attr_e( 'Поиск вакансий' ); ?>" value="<?php echo get_search_query(); ?>">

    <?php
    $terms_loaction = get_terms(
      array(
        'taxonomy' => 'location',
        'hide_empty' => false,
      )
    );
    ?>

    <?php
    if ( $terms_loaction ) :
      ?>
      <select name="city" class="select-block mobile-hide">
        <option value=""><?php esc_html_e( 'Город' ); ?></option>
        <?php
        foreach ( $terms_loaction as $location ) :
          ?>
          <option value="<?php echo esc_attr( $location->term_id ); ?>"><?php echo esc_html( $location->name ); ?></option>
        <?php endforeach; ?>
      </select>
    <?php endif; ?>

    <ul class="filter-list mobile-hide">
      <li>
        <label class="checkbox-block">
          <input type="checkbox" name="is_free_live">
          <span><?php esc_html_e( 'Бесплатное проживание' ); ?></span>
        </label>
      </li>
      ...
    </ul>
    <button type="submit" class="ajax-filter-btn btn"><?php esc_html_e( 'Найти вакансию' ); ?></button>
  </div>
  <input type="hidden" name="action" value="filter_vacancy">
</form>

add_action( 'wp_enqueue_scripts', function() {

  $my_args = array(
    'post_type' => 'offers',
    'posts_per_page' => -1,
    'tax_query' => array(
      'relation' => 'AND',
    ),
    'meta_query' => array(
      'relation' => 'AND',
    ),
  );

  $my_query = new WP_Query( $my_args );

  wp_register_script('ajax_js', get_stylesheet_directory_uri() . '/js/ajax.js', array('jquery'), time(), true);

  wp_localize_script( 'ajax_js', 'ajax_obj', array(
    'ajaxurl' => admin_url('admin-ajax.php'),
    'posts' => json_encode( $my_query->query_vars ),
    'current_page' => get_query_var( 'paged' ) ? get_query_var('paged') : 1,
    'max_page' => $my_query->max_num_pages,
  ) );

  wp_enqueue_script('ajax_js');
});

// FILTER
function filter_vacancy(){

  $args = array(
    'post_type' => 'offers',
    'posts_per_page' => -1,
    'tax_query' => array(
      'relation' => 'AND',
    ),
    'meta_query' => array(
      'relation' => 'AND',
    ),
  );

  if( !empty( $_POST['city'] ) && $_POST['city'] ) {
    $args['tax_query'][] = array(
      'taxonomy' => 'location',
      'field' => 'id',
      'terms' => $_POST['city'],
    );
  }

  if( isset( $_POST['is_free_equipment'] ) && $_POST['is_free_equipment'] ) {
    array_push($args['meta_query'][] = array(
        'key'         => 'is_free_equipment',
        'value'       => true,
        'compare'     => '=',
      )
    );
  }

  if( !empty( $_POST['s'] ) ) {
    $args['s'] = sanitize_text_field($_POST['s']);
  }

  query_posts( $args );

  global $wp_query;

  if ( have_posts() ) :
    ob_start();

    while ( have_posts() ) :
      the_post();
      get_template_part( 'template-parts/offers/offers', 'list' );
    endwhile;
    $response = ob_get_contents();
    ob_end_clean(); 
  else:
    $response = 'По запросу нет вакансий';
  endif;

  echo json_encode( array(
    'posts'       => json_encode( $wp_query->query_vars ),
    'max_page'    => $wp_query->max_num_pages,
    'found_posts' => $wp_query->found_posts,
    'content'     => $response,
  ) );
  die();
}
add_action('wp_ajax_filter_vacancy', 'filter_vacancy');
add_action('wp_ajax_nopriv_filter_vacancy', 'filter_vacancy');

$('#filter').on('submit', function (e) {
  e.preventDefault();
  var filter = $(this);
  $.ajax({
    type: 'POST',
    url: ajax_obj.ajaxurl,
    data: filter.serialize(),
    dataType : 'json',
    beforeSend: function(xhr){

    },
    success: function (data) {
      $('.offers-list').html(data.content);
      ajax_obj.posts = data.posts;
    },
  });
});

function custom_scripts_init() {

	// общие стили
	wp_enqueue_style( 'common-styles', get_theme_file_uri( 'assets/css/common.min.css' ) , array(), filemtime( get_theme_file_path( '/assets/css/common.min.css' ) ) );

	// общие скрипты 
	wp_enqueue_script( 'common-scripts', get_theme_file_uri( 'assets/js/common.min.js' ), array( 'jquery' ), filemtime( get_theme_file_path( '/assets/js/common.min.js' ) ), true );

	// скрипты для страницы постов
	if ( is_home() ) {
		wp_enqueue_script( 'home-scripts', get_theme_file_uri( 'assets/js/home.min.js' ), array( 'jquery' ), filemtime( get_theme_file_path( '/assets/js/home.min.js' ) ), true );
	}

	// скрипты для массива страниц
	if ( is_page( ['sample-page', 'contacts'] ) ) {
		wp_enqueue_script( 'page-scripts', get_theme_file_uri( 'assets/js/page.min.js' ), array( 'jquery' ), filemtime( get_theme_file_path( '/assets/js/page.min.js' ) ), true );
	}

}
add_action( 'wp_enqueue_scripts', 'custom_scripts_init' );

if ( is_home() || is_front_page() ) :
// тут то, что надо отображать только на главной
endif;