[CentOS] unable to run php application on centos4.0

> Php is installed on the system and in the httpd.conf file I have added
> index.php for Directory Index but whenever I try to access the blog i
> get the contents of the file and php is not executing.

eh? Why did you add index.php to the directory index setting? This is
all taken care of within the php package.

>
> The permissions on the directory under /var/www/html/blog is set to
> 777 but still the problem is persisting.

777 is a bad set of permissions for a web app. Standard web
permissions are usually 644 or 755. giving world writeable permissions
(777) on a php app is basically like handing a bum the keys to your
car.

> What should I do and where to check ?

Look in /var/log/httpd/error_log and see what it's complaining about.

-- 
During times of universal deceit, telling the truth becomes a revolutionary act.
George Orwell