id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc
13757,Passing functions as call by ref parameter should be avoided,TobiasBg,westi,"I recently had a bug report for a plugin, where script execution was stopped at an avoidable warning.

The problem was a call similar to
{{{
$my_array = array( ... );
$last_element_index = array_pop( array_keys( $my_array ) );
}}}

The reason for the issue is that the parameter for {{{array_pop()}}} is passed as a call by reference parameter. This leads to a problem here, because {{{array_keys( $my_array )}}} is not a variable that could be changed during the call by reference process (in this case, the last element can not be removed from the array).
This raises a warning by PHP (also documented at www.php.net/array_pop), and there are hosts that seem to be stopping PHP execution at such warning.

Fixing the issue is very easy by adding a variable:
{{{
$my_array = array( ... );
$_my_array_keys = array_keys( $my_array );
$last_element_index = array_pop( $_my_array_keys );
}}}

As I had this issue in my plugin, I also grep'ed WP core and found two instances of {{{array_pop( array_keys() )}}}:

- admin-ajax.php (line 893)

- ms-edit.php (line 107)

With {{{array_pop( explode() )}}}:

- wp-app.php (line 226)


With {{{array_pop( split() )}}}:

- atomlib.php (lines 151 and 230)

There are more functions (especially within {{{array_*}}}) that are affected, and that should be checked on whether a function call is passed where a call by ref parameter is expected.",defect (bug),closed,normal,3.3,Warnings/Notices,,normal,fixed,has-patch,