On Firefox I get the following below the footer

`Performance Optimization WordPress Plugins by W3 EDGE

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'Array' was given in /somedirectories/wordpress/wp-includes/plugin.php on line 405`

On Chrome it works fine and the last line on the footer is

Performance Optimization WordPress Plugins by W3 EDGE

1 Answer 1


This is not an error, it is a warning. You can make this go away by:

  • Fixing the warning
  • Write errors to the error log instead of the screen ( best practice )

To fix the error, I recommend looking at what's hooking into wp_footer etc, or using a PHP debugger

  • I have put /* All errors and warnings to file, instead of html screen */ define('WP_DEBUG_LOG', false); define('WP_DEBUG_DISPLAY', false); In the wp-config.php, but I still get warnings in the footer, when I use Firefox.
    – Siddharth
    Jun 28, 2012 at 17:17
  • 1
    This is a PHP setting you need to make, the wordpress constants can't always be relied upon, they work on some server configurations but not others
    – Tom J Nowell
    Jun 29, 2012 at 9:17

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