WordPress 后台文章列表添加自定义字段过滤筛选

add_action('restrict_manage_posts','cpt_type_filter',10);

function location_filtering($post_type){

  if('my-custom-post' === $post_type){

    return; // 检查是否是我们需要的文章类型

  }

  $selected = '';

  $request_attr = 'my_loc';

  if ( isset($_REQUEST[$request_attr]) ) {

    $selected = $_REQUEST[$request_attr];

  }

   // 需要筛选的 meta key

   $meta_key = 'my_custom_field_location';

   // 获取筛选条件数据

   global $wpdb;

   $results = $wpdb->get_col( 

   $wpdb->prepare( "

     SELECT DISTINCT pm.meta_value FROM {$wpdb->postmeta} pm

     LEFT JOIN {$wpdb->posts} p ON p.ID = pm.post_id

     WHERE pm.meta_key = '%s'

     AND p.post_status IN ('publish', 'draft')

     ORDER BY pm.meta_value", 

     $meta_key

   ) 

  );

   // 使用获取的筛选条件数据添加下拉表单

   echo '<select id="my-loc" name="my_loc">';

   echo '<option value="0">' . __( 'Show all locations', 'my-custom-domain' ) . ' </option>';

   foreach($results as $location){

     $select = ($result->ID == $selected) ? ' selected="selected"':'';

     echo '<option value="'.$location.'"'.$select.'>' . $location . ' </option>';

   }

   echo '</select>';

}

add_filter( 'parse_query', 'filter_request_query' , 10);

function filter_request_query($query){

    // 只修改后台文章列表页面的主查询

    if( !(is_admin() AND $query->is_main_query()) ){ 

      return $query;

    }

    // 如果不是我们需要查询的文章类型，并且设置了自定义查询参数，返回原始查询

    if( !'my-custom-post' === $query->query['post_type'] or !isset($_REQUEST['my_loc']) ){

      return $query;

    }

    // 如果自定义筛选条件是默认值，返回原始查询

    if(0 == $_REQUEST['my_loc']){

      return $query;

    }

   // 修改查询参数

    $query->query_vars = array(array(

      'field' => 'my_custom_field_location',

      'value' => $_REQUEST['my_loc'],

      'compare' => '=',

      'type' => 'CHAR'

    ));

    // 返回修改后的查询

    return $query;

  }