致命错误：调用未定义的函数

Question

I am trying to call a function which is defined in functions.php. But I can't figure out why this error is coming.

Let me tell you in detail what I am trying to accomplish: there are two header files — client and admin. The client header will be accessed when the user enters into a page through index.php, but admin header will be accessed after an admin successfuly logged in.

In the functions.php this is the function I have defined:

function get_my_header(){
  if(is_home()){ 
    get_header('client'); 
  }
  elseif(is_page('dashboard')){ 
    get_header('own'); 
  }
}

from index.php get_my_header() is called with no error but when I try to access the same function from the admin page I am getting this error:

Fatal error: Call to undefined function get_my_header()

The page where this error is coming has only this one line:

<?php get_my_header(); ?>

Answer 1

The most common causes of this are:

• The file you think is being included, isn't being included.
• Your calling the function prior to including the file

Based on your description as a header a file - I think the first is most likely. As you also mention that it's in an admin page that it doesn't work on - does the admin page live in a sub directory eg:

httpdocs/
   index.php
   admin/
       admin_index.php

If it does - the file path to the include file may be wrong, depending on your error_reporting() settings you may or may not be alerted to this.

One way to debug this would be to use require() instead of include() on the functions file - as that creates a fatal error if PHP can't find the script.

http://php.net/manual/en/function.require.php