upgrade php 5.3 to 5.6 - centos

PHP 5.6 is not provided by CentOS. It appears that the third-party Remi repository does provide packages for PHP 5.6 on CentOS. However, I can't personally vouch for the stability or trustworthiness of this source. I would recommend seeking out some opinions about that before jumping in and adding it as a package source.

You should also verify that ISPconfig and any other applications you are using are compatible with 5.6.

Can we use any other os like ubuntu which supports latest php ?

You can use any distro you would like. Both Ubuntu and Debian support PPAs of which I've seen PHP5.6.

This article has instructions for Ubuntu: http://tecadmin.net/install-php5-on-ubuntu/

Both Ubuntu 15.04 and 15.10 include PHP 5.6 in main. These are not LTS releases, so they are only supported for 9 months. Without knowing why you want to use PHP 5.6, it's difficult to give a recommendation.

We are using it for a web based application. 9 months support is good for us.

We can upgrade the server anytime.

will the ISPConfig work with 5.6?