在wordpress插件中查询数据库

Question

我正在处理一个插件，我需要查询wordpress数据库中的自定义表，我正在使用此代码，但它不输出任何内容。

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/**
 * Plugin Name: My Plugin
 * Plugin URI: http://www.domian.com
 * Description: Complete engine for www.mydomian.com
 * Version: 1.0.0
 * Author: Bradley Fletcher
 * Author URI: http://www.domian.net
 * License: GPL2
 */
 
add_action('admin_menu', 'mrq');

function mrq() {
	
	add_menu_page('Partners', 'My Removals Quote', 'administrator', 'my-plugin-settings', 'mrq_settings_page', 'dashicons-admin-generic', '21', 'myremovalsquote');
}

function mrq_settings_page() {

	if (is_user_logged_in()) {

		global $wpdb;
		$customers = $wpdb->get_results("SELECT partner_id, partner_name, email_address, active FROM partners WHERE active ='yes' ORDER BY partner_id ASC");

		echo "<table>";
		
		foreach($customers as $customer) {

			echo "<tr>";
			echo "<td>".$customer->partner_id."</td>";
			echo "<td>".$customer->partner_name."</td>";
			echo "</tr>";
		}

		echo "</table>";
	
	} else {
	
		echo "Sorry, only registered users can view this information";
	
	}
}

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