"php_flags" ignored with apache2 having suPHP enabled

I recently stumbled upon a problem regarding setting display_errors on/off on a webserver. One of the systems I maintain has configured apache2 with php5.x and suPHP module enabled. In this situation php_flags set in either the vhost or .htaccess files are not effective. Luckily i found out how to deal with that anyway: Just put a separate php.ini (maybe start with a copy from the system-wide one) in the documentroot of the vhost you try to set custom settings with! Voila. Now use that one for your special settings.