If you get an error, there is something in the error log. Maybe you have to look at a different log (/var/log/apache2/error.log ?) Looks like there was a php package, you should not have removed Compare the config of a working site (in /etc/apache2/sites-enabled) to one which is not working.
i checked the apt history and only kernel image is removed. i compared the working config of two sites server1.example.com and example.com. it looks too complicated for me, planning to restore from last week backup. thanks for all your help.
Is your problem related to this thread? You should not hijack old threads, instead create a new. Anyway, start with this: https://www.howtoforge.com/community/threads/please-read-before-posting.58408/
@Taleman: The message was an attempt to get around spam protection. The user and her messages have been removed.