Finally, i upgraded my OS version from Debian Etch to Debian Lenny.

And installed php-5.2.9 from source, everything went fine. Following are the steps i followed,

1. Installed apxs2 by installing the package,
apt-get install apache2-prefork-dev

2. configure
./configure --with-apxs2=/usr/bin/apxs2

3. make & install
make
make install

It said simple errors in the fly, as packages missing and so. Solving it straight away made the php-5.2.9 available by both cli & in web front end.

Thanks for all who have helped in solving the issue.