orderby 应为，例如。meta_value 或meta_value_num – 各种特定meta_type\'可按元数据订购。另外ameta_key 必须设置并显示在查询中。准确地说，为了避免误解，meta_key 必须是keyname 要排序的字段的。仔细查看Order & Orderby Parameters 和Custum Fields Parameters 第节WP_Query 有关详细信息，请参阅文档。

当您提交表单时，表单会自动将您的选择值添加到url。没有必要创造这样的价值&orderby=date&order=dsc. 若要在单个select值中传递多个信息，可以使用更简单的value和If语句。对于最新选项，我将使用newest as value和add做这样一个if语句。

// Url /?s=test&order=newest

$orderby = \'\';
$order = \'\';

// Get filtered $_GET[\'order\'] parameter
$value = filter_input( INPUT_GET, \'order\', FILTER_SANITIZE_STRING );

if( $value === \'newest\' ) {
    $orderby = \'date\';
    $order = \'desc\';
}

// Modify query using $orderby and $order parameters

// Url /?s=test&order=newest

// Get filtered $_GET[\'order\'] parameter
$value = filter_input( INPUT_GET, \'order\', FILTER_SANITIZE_STRING );
$selected = ($value === \'newest\') ? \'selected\': \'\' ;
?>

<select name="order">
    <option value="newest" <?php echo esc_attr( $selected ); ?>></option>
</select>

下面的代码是如何按邮件排序的完整示例date, price 和size. 处决wpse_288655_display_form 要在其中显示排序表单的函数。

/**
 * Display sort form
 */
function wpse_288655_display_form() {

    /**
     * Get all params from url which are not part of our sort form
     * and display it in form as hidden inputs.
     */
    $search_param = filter_input( INPUT_GET, \'s\', FILTER_SANITIZE_STRING );

    /**
     * Current order value to select proper field
     */
    $value = filter_input( INPUT_GET, \'order\', FILTER_SANITIZE_STRING );
    ?>

    <form method="get">
        <?php wpse_288655_display_select(\'order\', \'Sort by:\', wpse_288655_get_order_by_options(), $value ); ?>

        <?php
            /**
             * Display all params from url which do not apply to our sort form
             */
        ?>
        <input type="hidden" name="s" value="<?php esc_attr_e( $search_param ); ?>">

        <button type="submit"><?php esc_html_e(\'Sort\'); ?></button>
    </form>
    <?php
}

/**
 * Get sort options
 */
function wpse_288655_get_order_by_options(){

    return array(
        \'\' => \'\',
        \'newest\' => __(\'Newest\'),
        \'oldest\' => __(\'Oldest\'),
        \'most_expensive\' => __(\'Most Expensive\'),
        \'least_expensive\' => __(\'Least Expensive\'),
        \'largest\' => __(\'Largest\'),
        \'smallest\' => __(\'Smallest\'),
    );
}

/**
 * Display select field
 */
function wpse_288655_display_select( $name, $label, $options, $value = \'\' ) {
    ?>
    <label><?php esc_html_e( $label ) ?></label>
    <select name="<?php esc_attr_e( $name ) ?>">
        <?php wpse_288655_display_options( $options, $value ); ?>
    </select>
    <?php
}

/**
 * Display select options
 */
function wpse_288655_display_options( $options, $value ) {

    foreach( $options as $option_value => $option_label ):
        $selected = ( $option_value === $value ) ? \' selected\' : \'\';
        ?>
        <option value="<?php esc_attr_e( $option_value ) ?>"<?php esc_attr_e( $selected ) ?>><?php esc_html_e( $option_label ) ?></option>
        <?php

    endforeach;
}

/**
 * Sort posts using pre_get_posts filter
 */
function wpse_288655_order_posts( $query ) {

    /**
     * Execute query only when we are on search page and this is main query
     */
    if ( $query->is_search() && $query->is_main_query() ) {

        $value = filter_input( INPUT_GET, \'order\', FILTER_SANITIZE_STRING );
        $order_by_options = wpse_288655_get_order_by_options();

        if( isset( $order_by_options[ $value ] ) && !empty( $value ) ) {

            switch( $value ) {
                case \'newest\':

                    $query->set( \'order\', \'desc\' );
                    $query->set( \'orderby\', \'date\' );

                    break;

                case \'oldest\':

                    $query->set( \'order\', \'asc\' );
                    $query->set( \'orderby\', \'date\' );

                    break;
                case \'most_expensive\':

                    $query->set( \'meta_key\', \'price\' ); // Your custom meta_key

                    $query->set( \'order\', \'desc\' );
                    $query->set( \'orderby\', \'meta_value_num\' );

                    break;
                case \'least_expensive\':

                    $query->set( \'meta_key\', \'price\' ); // Your custom meta_key

                    $query->set( \'order\', \'asc\' );
                    $query->set( \'orderby\', \'meta_value_num\' );

                    break;
                case \'largest\':

                    $query->set( \'meta_key\', \'size\' ); // Your custom meta_key

                    $query->set( \'order\', \'desc\' );
                    $query->set( \'orderby\', \'meta_value_num\' );

                    break;
                case \'smallest\':

                    $query->set( \'meta_key\', \'size\' ); // Your custom meta_key

                    $query->set( \'order\', \'asc\' );
                    $query->set( \'orderby\', \'meta_value_num\' );

                    break;
                default:
                    break;
            }
        }
    }
}

add_filter(\'pre_get_posts\', \'wpse_288655_order_posts\');

因为下面的答案看起来很不确定-例如，你不能仅仅挂钩pre_get_posts 因为它会影响网站上的每个查询，甚至在WordPress管理区域。

我给您的第一个建议是拒绝使用JavaScript，我希望您的下拉列表如下所示：

<form action="" method="GET"><select name="sortposts">
    <option disabled>Sort by</option>
    <option value="date-DESC">Newest</option>
    <option value="date-ASC">Oldest</option>
    <option value="property_price-ASC">Most Expensive</option>
    <option value="property_price-DESC">Least Expensive</option>
.....

<?php
    global $wp_query;

    // let\'s create new array with args
    if( !empty( $_GET[\'sortposts\'] ) ) {
        // I recommend to explode it because we\'re take 2 param values from one $_GET variable
        $sort_args = explode( "-", $_GET[\'sortposts\'] );
        // $sort_args[0] is what we sort
        // $sort_args[1] is how we sort - Ascending or Descending
        $new_args[\'order\'] = $sort_args[1];
        if( $sort_args[0] == \'date\' ) {
            // date is a default WP_Query value, so we do nothing
            $new_args[\'orderby\'] == \'date\';
        } elseif( $sort_args[0] == \'property_price\' ) {
            $new_args[\'orderby\'] = \'meta_value_num\';
            $new_args[\'meta_key\'] = \'THIS IS A PROPERTY PRICE META KEY\';
        }
    }

    $args = array_merge( $wp_query->query_vars, $new_args );
    query_posts( $args );

如果您想用AJAX实现过滤，也可以看看本教程https://rudrastyh.com/wordpress/ajax-load-more-with-filters.html