Wordpress自定义插件wpdb无法识别

Question

I'm developing my first wordpress plugin where I can list all my employees with some CRUD functionality.

When I click "Add Employee" I get a new window where I can fill in all the fields for an employee and after that I click "Save"

But when I click save I get the following PHP error:

   Fatal error: Call to a member function insert() on a non-object in C:\wamp\www\wp-custom-plugin\wp-content\plugins\werknemers\employee_crud_functions.php on line 15

And when I look at line 15 the code is:

 $wpdb->insert( ... )

and this is my form with the action set to that php page

 <form method="POST" action="<?php bloginfo('url') ?>/wp-content/plugins/werknemers/employee_crud_functions.php">

I assume that the file is not aware of the $wpdb variable. But how can I let that php page know what it is? Or am I using it all wrong?

Answer 1

You are quite possibly missing the global declaration of $wpdb.

From the wpdb reference.

WordPress provides a global variable, $wpdb, 
which is an instantiation of the class already 
set up to talk to the WordPress database. 
Always use the global $wpdb variable. 
(Remember to globalize $wpdb before using it in any custom functions.)

You need to use it like this.

global $wpdb;
//do something with it.