Please Let me know -- How to Install mantis on Redhat Linux OS ( Step by Step )

Friends,

I was installed mantis last 1yr back .. still now its working fine ... but last month our test server is Crashed and lost the mantis ... its bad for me , here we don't have System  Admin , i have to do it as soon as possible.

Now i had done Installation i thing so ... Please let u know what i did now ...

1. Apache web Server its default installed thr Redhat Linux
2. PHP installed
3. Mysql Installed
4. finally i have backup for previous mantis, & deployed in Appache2 under htdoc
5. Changed the Conf file for mantis for database setup

Issues is : i thing PHP is not supporting , when am using mantis ... it showing all the PHP files when i clicked on it .. its asking for download ...

So Please let me know .... what i can do further