Building An Advanced WordPress Search With WP_Query https://www.smashingmagazine.com/2016/03/advanced-wordpress-search-with-wp_query/

smashing-plugin.php

<?php
/**
 * @package Smashing_plugin
 * @version 1.0
 */
/*
Plugin Name: Smashing plugin
Plugin URI: https://www.smashingmagazine.com/2016/03/advanced-wordpress-search-with-wp_query/
Description: This is an example plugin for Smashing Magazine readers.
Author: Carlo Daniele
Version: 1.0
Author URI: http://carlodaniele.it/en/
*/

/**
 * Plugin setup
 * Register post type and shortocode
 */
function sm_setup() {

	$labels = array(
		'name' => __( 'Accommodation', 'smashing_plugin' ),
		'singular_name' => __( 'Accommodation', 'smashing_plugin' ),
		'add_new_item' => __( 'Add New Accommodation', 'smashing_plugin' )
		);

	$args = array(
		'labels' => $labels,
		'description' => '',
		'public' => true,
		'show_ui' => true,
		'has_archive' => true,
		'show_in_menu' => true,
		'exclude_from_search' => false,
		'capability_type' => 'post',
		'map_meta_cap' => true,
		'hierarchical' => false,
		'rewrite' => array( 'slug' => 'accommodation', 'with_front' => true ),
		'query_var' => true,
		'menu_icon' => 'dashicons-admin-multisite',		
		'supports' => array( 'title', 'editor', 'thumbnail', 'author', 'custom-fields'  ),
		'register_meta_box_cb' => 'sm_add_meta_boxes',
		'taxonomies' => array( 'typology' )
	);
	register_post_type( 'accommodation', $args );

	add_shortcode( 'sm_search_form', 'sm_search_form' );
}

add_action( 'init', 'sm_setup' );

/**
 * Register custom taxonomy
 */
function sm_register_custom_taxonomies() {

	$labels = array(
		'name' => __( 'Typologies', 'smashing_plugin' ),
		'label' => __( 'Typologies', 'smashing_plugin' ),
		'add_new_item' => __( 'Add new Typology', 'smashing_plugin' ),
		);

	$args = array(
		'labels' => $labels,
		'hierarchical' => true,
		'label' => __( 'Typologies', 'smashing_plugin' ),
		'show_ui' => true,
		'query_var' => true,
		'rewrite' => array( 'slug' => 'typology', 'with_front' => true ),
		'show_admin_column' => true,
	);
	register_taxonomy( 'typology', array( 'accommodation' ), $args );

} 

add_action( 'init', 'sm_register_custom_taxonomies' );

/**
 * Add custom meta boxes
 */
function sm_add_meta_boxes(){
	add_meta_box( 'sm_features_meta_box', __( 'Features', 'smashing_plugin' ), 'sm_build_features_meta_box', 'accommodation', 'side' );
	add_meta_box( 'sm_location_meta_box', __( 'Location', 'smashing_plugin' ), 'sm_build_location_meta_box', 'accommodation', 'normal' );
}

/**
 * Print custom meta box
 */
function sm_build_features_meta_box( $post ){
	// make sure the form request comes from WordPress
	wp_nonce_field( basename( __FILE__ ), 'sm_features_meta_box_nonce' );
	// retrieve current field values
	$type = get_post_meta( $post->ID, '_sm_accommodation_type', true );
	$facilities = get_post_meta( $post->ID, '_sm_accommodation_facilities', false );

	// an array of default facilities
	$available_facilities = array( 'essentials', 'kitchen', 'internet', 'parking', 'tv', 'washer', 'wireless' );
	
	?>
	<div class='inside'>

		<p><strong>Type of accommodation</strong></p>

		<p>
			<select name="customfields[type]">
                <option value="" <?php selected( $type, "" ); ?>>Select</option>
                <option value="entire" <?php selected( $type, 'entire' ); ?>><?php _e( 'Entire house', 'smashing_plugin' ); ?></option>
                <option value="private" <?php selected( $type, 'private' ); ?>><?php _e( 'Private room', 'smashing_plugin' ); ?></option>
                <option value="shared" <?php selected( $type, 'shared' ); ?>><?php _e( 'Shared room', 'smashing_plugin' ); ?></option>
            </select>
		</p>

		<p><strong><?php _e( 'Facilities', 'smashing_plugin' ); ?></strong></p>
		<p>
			<?php
				
				foreach ( $available_facilities as $f ) {
					if( !isset( $facilities[0][$f] ) ){
						$facilities[0][$f] = 0;
					}
					?>
					<input type="checkbox" name="customfields[facilities][<?php echo $f; ?>]" value="<?php echo $f; ?>" <?php checked( $facilities[0][$f], $f ); ?>><?php echo ucfirst($f); ?><br />
					<?php
				}
			?>
		</p>
	</div>
	<?php
}

/**
 * Print custom meta box
 */
function sm_build_location_meta_box( $post ){

	wp_nonce_field( basename( __FILE__ ), 'sm_location_meta_box_nonce' );

	$custom_fields = get_post_custom( $post->ID );

	$address = isset( $custom_fields['_sm_accommodation_address'][0] ) ? $custom_fields['_sm_accommodation_address'][0] : '';
	$city = isset( $custom_fields['_sm_accommodation_city'][0] ) ? $custom_fields['_sm_accommodation_city'][0] : '';
	$country = isset( $custom_fields['_sm_accommodation_country'][0] ) ? $custom_fields['_sm_accommodation_country'][0] : '';
	
	?>
	<div class="inside">
		<p><strong>Address</strong></p>
		<p><input type="text" id="sm_accommodation_address" name="customfields[address]" value="<?php echo esc_attr( $address ); ?>" /></p>

		<p><strong>City</strong></p>
		<p><input type="text" id="sm_accommodation_city" name="customfields[city]" value="<?php echo esc_attr( $city ); ?>" /></p>

		<p><strong>Country</strong></p>
		<p><input type="text" id="sm_accommodation_country" name="customfields[country]" value="<?php echo esc_attr( $country ); ?>" /></p>
	</div>
	<?php
}

/**
 * Store custom meta box data
 */
function sm_save_meta_boxes_data( $post_id ){
	// verify first meta box nonce
	if ( !isset( $_POST['sm_features_meta_box_nonce'] ) || !wp_verify_nonce( $_POST['sm_features_meta_box_nonce'], basename( __FILE__ ) ) ){
		return;
	}
	// verify second meta box nonce
	if ( !isset( $_POST['sm_location_meta_box_nonce'] ) || !wp_verify_nonce( $_POST['sm_location_meta_box_nonce'], basename( __FILE__ ) ) ){
		return;
	}
	// return if autosave
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ){
		return;
	}

	// Check the user's permissions.
	if ( isset( $_POST['post_type'] ) && 'accommodation' == $_POST['post_type'] ) {

		if ( ! current_user_can( 'edit_post', $post_id ) ){
			return;
		}
	}

	// custom fields values   
    $customfields = ( isset( $_POST['customfields'] ) ) ? (array) $_POST['customfields'] : array();
    
    if( count( $customfields ) == 0 ){
		return;
	}

    foreach ($customfields as $key => $value) {

    	// checks if is bidimensional array
    	// and sanitize values
    	if( is_array( $value ) ){

    		$value = array_map( 'sanitize_text_field', $value );

    	// if not an array
    	// sanitize value
    	}else{
    		
    		$value = sanitize_text_field( $value );
    	
    	}

    	update_post_meta( $post_id, '_sm_accommodation_' . $key, $value );

    }

}
add_action( 'save_post', 'sm_save_meta_boxes_data' );



/**
 * Register custom query vars
 *
 * @link https://codex.wordpress.org/Plugin_API/Filter_Reference/query_vars
 */
function sm_register_query_vars( $vars ) {
    $vars[] = 'type';
    $vars[] = 'city';
    return $vars;
} 
add_filter( 'query_vars', 'sm_register_query_vars' );

/**
 * Build a custom query based on several conditions
 * The pre_get_posts action gives developers access to the $query object by reference
 * any changes you make to $query are made directly to the original object - no return value is requested
 *
 * @link https://codex.wordpress.org/Plugin_API/Action_Reference/pre_get_posts
 *
 */
function sm_pre_get_posts( $query ) {
	// check if the user is requesting an admin page 
	// or current query is not the main query
	if ( is_admin() || ! $query->is_main_query() ){
		return;
	}

	// edit the query only when post type is 'accommodation'
	// if it isn't, return
	if ( !is_post_type_archive( 'accommodation' ) ){
		return;
	}

    $meta_query = array();


	// get query var values
	// defaults to empty string
    if( !empty( get_query_var( 'city' ) ) ){
    	$meta_query[] = array( 'key' => '_sm_accommodation_city', 'value' => get_query_var( 'city' ), 'compare' => 'LIKE' );
    }
	if( !empty( get_query_var( 'type' ) ) ){
		$meta_query[] = array( 'key' => '_sm_accommodation_type', 'value' => get_query_var( 'type' ), 'compare' => 'LIKE' );
	}
    if( count( $meta_query ) > 1 ){
       	$meta_query['relation'] = 'AND';
    }
    if( count( $meta_query ) > 0 ){
    	$query->set( 'meta_query', $meta_query );
    }
}
add_action( 'pre_get_posts', 'sm_pre_get_posts', 1 );


/**
 * Build search form markup
 */
function sm_search_form( $args ){

	// The Query
    // meta_query expects nested arrays, even if you only have one query
    // to add the category param
    $sm_query = new WP_Query( array( 'post_type' => 'accommodation', 'posts_per_page' => '-1', 'meta_query' => array( array( 'key' => '_sm_accommodation_city' ) ) ) );

    // The Loop
    if ( $sm_query->have_posts() ) {
        $cities = array();
        while ( $sm_query->have_posts() ) {
            $sm_query->the_post();
            $city = get_post_meta( get_the_ID(), '_sm_accommodation_city', true );

            // populate an array of all occurrences (non duplicated)
            if( !in_array( $city, $cities ) ){
                $cities[] = $city;    
            }
        }
    }

    /* Restore original Post Data */
    wp_reset_postdata();

    if( count($cities) == 0){
        return;
    }
    asort($cities);
    
    $select_city = '<select name="city">';
    $select_city .= '<option value="">' . __( 'Select city', 'smashing_plugin' ) . '</option>';
    foreach ($cities as $city ) {
        $select_city .= '<option value="' . $city . '">' . $city . '</option>';
    }
    $select_city .= '</select>' . "\n";

    reset($cities);

    
    $args = array( 'hide_empty' => false );
    $typology_terms = get_terms( 'typology', $args );
    if( is_array( $typology_terms ) ){
    	$select_typology = '<select name="typology">';
    	$select_typology .= '<option value="" selected="selected">' . __( 'Select typology', 'smashing_plugin' ) . '</option>';
    	foreach ( $typology_terms as $term ) {
    		$select_typology .= '<option value="' . $term->slug . '">' . $term->name . '</option>';
    	}
    	$select_typology .= '</select>' . "\n";
    }

    $select_type = '<select name="type">';
    $select_type .= '<option value="" selected="selected">' . __( 'Select room type', 'smashing_plugin' ) . '</option>';
    $select_type .= '<option value="entire">' . __( 'Entire house', 'smashing_plugin' ) . '</option>';
    $select_type .= '<option value="private">' . __( 'Private room', 'smashing_plugin' ) . '</option>';
    $select_type .= '<option value="shared">' . __( 'Shared room', 'smashing_plugin' ) . '</option>';
    $select_type .= '</select>' . "\n";


    $output = '<form id="smform" action="' . esc_url( home_url() ) . '" method="GET" role="search">';
    $output .= '<div class="smtextfield">' . '<input type="text" name="s" placeholder="Search key..." value="' . get_search_query() . '" /></div>';
    $output .= '<div class="smselectbox">' . $select_city . '</div>';
    $output .= '<div class="smselectbox">' . $select_typology . '</div>';
    $output .= '<div class="smselectbox">' . $select_type . '</div>';
    $output .= '<input type="hidden" name="post_type" value="accommodation" />';
    $output .= '<p><input type="submit" value="Go!" class="button" /></p></form>';

    return $output;
}