Cannot redeclare previously declared ambiguity

[jabcreations]

Description

From an error.log report:

[22-Sep-2026 18:51:21 UTC] PHP Fatal error: Cannot redeclare example() (previously declared in D:\wamp\errors.php:11) in D:\wamp\errors.php on line 11

This ambiguous error has wasted a lot of developer's precious time. It tells us where the function is declared but it fails to tell us where the file is included a second time. This results in developers opting to use include_once() instead of include() and tracking down errors in logic.

A proper fix applied to the same scenario should result in the following error report:

[22-Sep-2026 18:51:21 UTC] PHP Fatal error: Cannot redeclare example() from D:\wamp\test.php:427 (previously declared in D:\wamp\errors.php:11) in D:\wamp\errors.php on line 11

PHP Version

PHP 8.3.32

Operating System

No response

[jabcreations]

For those dealing with this issue I found a work-around until this bug is squashed (do not blindly copy/paste):

<?php

// 1. Function already exists on this file but this line only triggers on the second/erroneous call:
if (function_exists('error_report'))
{
 // 2. Force capture of stack call into a string:
 ob_start();
 debug_print_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
 $st = array_filter(preg_split('/\R/', ob_get_clean()));

 $clean = '';
 // 3. Set your $path, so public_html/admin/index.php would be explode('admin', etc:
 $path = explode('[_______subdirectory_goes_here________]', __FILE__)[0];

 foreach ($st as $l)
 {
  $p = explode($path, $l);
  if (strlen($clean) > 0) {$clean .='; ';}
  $clean .= ((isset($p[1])) ? $p[1] : $l);
 }

 // 4. A clean error report including the proper stack trace so now you know *exactly* what called what:
 trigger_error('DOUBLE INCLUDE _0_header_02_errors.php blocked! from '.$clean.'.', E_USER_WARNING);
 
 return;
}

//Functions that get double-called below here.
?>

This should work regardless of whether your error handler is handling this or it gets dumped in to your error.log (that you changed from error_log (why?!) in your php.ini configuration file.