问如何连接变量以搜索结果标题？

EN

// Display Fields
add_action('woocommerce_product_options_general_product_data', 'woocommerce_product_custom_fields');
// Save Fields
add_action('woocommerce_process_product_meta', 'woocommerce_product_custom_fields_save');

function woocommerce_product_custom_fields() {
    global $woocommerce, $post;
    echo '';
    // Custom Product Text Field 1
    woocommerce_wp_text_input(
        array(
            'id' => '_tyre_size_field',
            'placeholder' => 'Tyre Size',
            'label' => __('Tyre Size', 'woocommerce'),
            'desc_tip' => 'true'
        )
    );
    // Custom Product Text Field 2
    woocommerce_wp_text_input(
        array(
            'id' => '_load_speed_field',
            'placeholder' => 'Load Index & Speed Rating',
            'label' => __('Load Index & Speed Rating', 'woocommerce'),
            'desc_tip' => 'true'
        )
    );
    // Custom Product Text Field 3
    woocommerce_wp_text_input(
        array(
            'id' => '_tyre_brand_field',
            'placeholder' => 'Tyre Brand',
            'label' => __('Tyre Brand', 'woocommerce'),
            'desc_tip' => 'true'
        )
    );
    // Custom Product Text Field 4
    woocommerce_wp_text_input(
        array(
            'id' => '_brand_model_field',
            'placeholder' => 'Brand Model',
            'label' => __('Brand Model', 'woocommerce'),
            'desc_tip' => 'true'
        )
    );
    // Custom Product Text Field 5
    woocommerce_wp_select( array(
        'id'          => '_run_flat_field',
        'label'       => __( 'Run Flat or Non-Run Flat', 'woocommerce' ),
        'description' => __( 'Choose whether the tyre is run-flat or non-run flat.', 'woocommerce' ),
        'desc_tip'    => true,
        'options'     => array(
            ' '        => __( ' ', 'woocommerce' ),
            'RUN FLAT'    => __('RUN FLAT', 'woocommerce' ),
            'NON-RUN FLAT' => __('NON-RUN FLAT', 'woocommerce' ),
        )
    ) );
    echo '';
}

function woocommerce_product_custom_fields_save($post_id) {
    // Custom Product Text Field 1
    $woocommerce_custom_product_tyre_size_field = $_POST['_tyre_size_field'];
    if (!empty($woocommerce_custom_product_tyre_size_field))
        update_post_meta($post_id, '_tyre_size_field', esc_attr($woocommerce_custom_product_tyre_size_field));
    // Custom Product Text Field 2
    $woocommerce_custom_product_tyre_brand_field = $_POST['_tyre_brand_field'];
    if (!empty($woocommerce_custom_product_tyre_brand_field))
        update_post_meta($post_id, '_tyre_brand_field', esc_attr($woocommerce_custom_product_tyre_brand_field));
    // Custom Product Text Field 3
    $woocommerce_custom_product_brand_model_field = $_POST['_brand_model_field'];
    if (!empty($woocommerce_custom_product_brand_model_field))
        update_post_meta($post_id, '_brand_model_field', esc_attr($woocommerce_custom_product_brand_model_field));
    // Custom Product Text Field 4
    $woocommerce_custom_product_run_flat_field = $_POST['_run_flat_field'];
    if (!empty($woocommerce_custom_product_run_flat_field))
        update_post_meta($post_id, '_run_flat_field', esc_attr($woocommerce_custom_product_run_flat_field));
    // Custom Product Text Field 5
    $woocommerce_custom_product_load_speed_field = $_POST['_load_speed_field'];
    if (!empty($woocommerce_custom_product_load_speed_field))
        update_post_meta($post_id, '_load_speed_field', esc_attr($woocommerce_custom_product_load_speed_field));
}

function concatenate_fields_to_title( $title ) {
    global $post;
    $text1 = get_post_meta( $post->ID, '_tyre_size_field', true );
    $text2 = get_post_meta( $post->ID, '_load_speed_field', true );
    $text3 = get_post_meta( $post->ID, '_tyre_brand_field', true );
    $text4 = get_post_meta( $post->ID, '_brand_model_field', true );
    $text5 = get_post_meta( $post->ID, '_run_flat_field', true );
    if (stripos( $title, 'TYRE' ) == true ) {
    return $text1 . " ". $text2 . " " . $text3 . " " . $text4 . " " . $text5 . " " . $title;
    }
    return $title;
}

add_filter( 'the_title', 'concatenate_fields_to_title' );