current_user_can()

[merianos]

I use the function current_user_can() and then I get the error

Fatal error: Call to undefined function wp_get_current_user() in D:\VirtualHost\www.wordpress3.dch\www\wp-content\plugins\my_plugin\includes\init.php on line 5

the function is used into a plugin of mine.

[nacin]

You're using it too early.

You need to wait until the current user is set up, which means about the init hook.

For more, try the support forums: ​http://wordpress.org/support/.