如何在这样的查询中计算帖子：

$countPosts = ???????
$tires = get_posts(array(
    'numberposts'   => $countPosts,
    'post_type'     => 'tires',
    'meta_query'    => array(
       'relation'       => 'AND',
        array(
            'key'       => 'tire_width',
            'value'     => '175',
            'compare'   => '=',
        ),
        array(
            'key'       => 'tire_height',
            'value'     => '70',
            'compare'   => '=',
        ),

    ),
));

我需要分页的职位总数