如何动态构建分类查询？

我有以下代码用于动态创建颜色和价格数组：

$color = $_POST[\'color\'];
$price = $_POST[\'price\'];

if (!empty($color)) {
    $query_color =  array(
                        \'taxonomy\' => \'color\',
                        \'field\' => \'term_id\',
                        \'terms\' => $color
        );
} else {
    $query_color = array(
                    \'taxonomy\' => \'color\',
                    \'field\' => \'term_id\',
                    \'terms\' => \'\'
    );
}

if (!empty($price)) {
    $query_price =  array(
                        \'taxonomy\' => \'price\',
                        \'field\' => \'term_id\',
                        \'terms\' => $color
        );
} else {
    $query_price = array(
                    \'taxonomy\' => \'price\',
                    \'field\' => \'term_id\',
                    \'terms\' => \'\'
    );
}

我有一个查询代码：

$args = array(
        \'s\' => $search,
        \'post_type\' => array( \'post\' ),
        \'posts_per_page\' => 99999,
        \'tax_query\' => array(
            \'relation\' => \'OR\',
            $query_color,
            $query_price,
        )
);
$wp_query = new WP_Query( $args );

但是，效果不好。它总是显示所有帖子广告，而不仅仅是$color和$price数组中的内容。知道我做错了什么吗？

$args = array( .....,
    \'tax_query\' => array( \'relation\' => \'OR\' ),
    ... );

if( $_GET[\'color\'] )
    $args[\'tax_query\'][] = array(
        \'taxonomy\' => \'color\',
        \'field\' => \'term_id\',
        \'terms\' => $color
    );