If you are upgrading PHP from 5.3 to 5.4 for an existing application, you can use the following commands to check for parse errors.
The output is really what comes out of stderr, which will be the parse errors.
Be sure to check out the short_open_tag directive (http://www.php.net/manual/en/ini.core.php#ini.short-open-tag).
By default <?= is enabled, to use <? for statements other than echo, you must enable the short_open_tag option in /etc/php.ini.