PHP Warning raised from plugin.php on line 235

[nodeleaf]

Apache error log is recording the very same persistent error on every client connections:

PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'return "";' not found or invalid function name in /.../wp-includes/plugin.php on line 235

This error is filling about 99% of this production server's errors log file making critical errors more difficult to track and address: an heavy cost to pay if this was really about a missing return ""; PHP statement.

I am now using 4.5.3 but the issue is older than that as this error is logged repetively from many months.

[dd32]

This is likely coming from a plugin or theme you're running on your site.

It'll be caused by a plugin/theme doing something such as add_action( 'something', 'return "";' ); which is invalid usage of the function - I'd suggest you search for it by searching for the return ""; string on your site.

[nodeleaf]

It was in the theme:

add_filter('the_generator','return "";');

Replaced by:

add_filter('the_generator',create_function('$a','return "";'));

Thank you for your suggestion.

[DrewAPicture]

Replying to nodeleaf:

It was in the theme:

add_filter('the_generator','return "";');

Replaced by:

add_filter('the_generator',create_function('$a','return "";'));

Thank you for your suggestion.

FYI, core has utility functions you can use as callbacks in this sort of situation ;)

<?php
add_filter( 'the_generator', '__return_empty_string' );