How to install extension php?

$ sudo apt-get install extension_name
The above command install the specified extension in unix/linux box.

How to install intl extension php?

$ sudo apt-get install php5-intl

How to install PHP accelerator APC?

sudo apt-get install php-apc

The extension already installed then it will upgrade if any new version released.

If no latest version release after our installation then it show message like below

$ sudo apt-get install php-apc
[sudo] password for sasikala:
Reading package lists... Done
Building dependency tree
Reading state information... Done
php-apc is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 404 not upgraded.