I moved a WordPress site from one domain to another and there were a lot of white spaces that needed to be removed.

The only problem that is left are the following errors:

  • PHP Notice: Undefined offset: 0 in /home/linguist/public_html/test/wp-includes/plugin.php on line 767
  • PHP Notice: Undefined offset: 0 in /home/linguist/public_html/test/wp-includes/plugin.php on line 785

then further

PHP Warning: Cannot modify header information - headers already sent by (output started at /home/linguist/public_html/test/wp-includes/plugin.php:767)

Its all due to this code which hasn't been changed at all but is creating errors.

if (is_object($function[0]) ) {
    // Object Class Calling
    if ( function_exists('spl_object_hash') ) {
        return spl_object_hash($function[0]) . $function[1];
    } else {
        $obj_idx = get_class($function[0]).$function[1];
        if ( !isset($function[0]->wp_filter_id) ) {
            if ( false === $priority )
                return false;
            $obj_idx .= isset($wp_filter[$tag][$priority]) ? count((array)$wp_filter[$tag][$priority]) : $filter_id_count;
            $function[0]->wp_filter_id = $filter_id_count;
        } else {
            $obj_idx .= $function[0]->wp_filter_id;

        return $obj_idx;
} else if ( is_string($function[0]) ) {
    // Static Calling
    return $function[0].$function[1];


Could someone please help me with this?

  • You remove whitespaces? Where do you remove them? This code is throwing an error because it is called with a wrong parameter. So the real error is at another palce.
    – Ralf912
    Apr 12, 2013 at 11:50

3 Answers 3


Some code on your site registers a filter or an action with invalid arguments. The errors you see happen, because add_action() or add_filter() was called with a second argument that is not a string, an object or an array.


add_action( 'wp_head', NULL );
add_filter( 'the_content', -1 );

Disable all plugins, switch to Twenty Eleven, and re-enable everything until the errors comes back. Then find all calls to add_action() or add_filter().


You can find out which command is the reason. Add the following code before the line "if ( is_object( $function[0] ) ) {"


PHP Warning: Cannot modify header information - headers already sent by (output started at /home/linguist/public_html/test/wp-includes/plugin.php:767)

you just put ob_start() in your functions.php at the top of the line.

  • 4
    Hiding errors is wrong. They should be fixed instead.
    – fuxia
    Apr 12, 2013 at 11:47
  • 2
    The headers already sent error is caused by the output of the first error(s). So you can ignore this. If you fix the previous error(s), this error will also be gone.
    – Ralf912
    Apr 12, 2013 at 11:48

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