$ wpdb - 无法在插件表-Wordpress中计算no或注册用户

Question

I am using a plugin event Registration for wordpress. Everything just works fine. But I need to display the no of attendee or registered users in the page or widget.

I am using this code to display the no, but did not work..

<?php

global $wpdb;
$user_count = $wpdb->get_var( "SELECT COUNT(*) FROM $wpdb->evr_attendee" );
echo "<p>User count is {$user_count}</p>";

?>

This code works great if I replace evr_attendee with users. I observed , the code just works great for wordpress database tables and does not work for external plugins, Please Help.

Answer 1

$wpdb is an instance of the wpdb class, which is defined in wp-includes/wp-db.php. Those "table names" are actually variables defined inside the class.

This will work:

if (!isset($wpdb->tablename)) {
$wpdb->tablename = $table_prefix . 'tablename';
}

Or simply you can use:

SELECT COUNT(*) FROM your_table_prefix_evr_attendee