This is an attempt to share a Drupal 5 core patch that improves compatibility with PHP 5.3. Drupal 5 will officially not support PHP 5.3 (see), however some of us have no other choice and will have to make D5 work anyway.
Warning: You will have to patch many core/contributed modules as well, because of the severe PHP warning when a functions expects a reference parameter and a value is given; and the function will not be executed (example:). In most cases the solution is to simply remove the '&' reference operator from the parameter, if the function does not need the reference.
PHP errors are logged to watchdog (admin/logs/watchdog), so if you hit broken subpages of your site visit the log where you can find the broken functions that expect references.
The patch was inspired by