Required Modules installation and php.ini settings for running Symfony2,

=> Download Symfony2 package

=> Extract in your webdata/root folder and give name Symfony

=> Open Terminal/Command Line and go to project directory

=> First Download and Install Composer for Project Dependancies fire below commands

-> curl -s http://getcomposer.org/installer | php
-> php composer.phar install
-> sudo apache2ctl restart

=> sudo apt-get install php-apc [Install module for Alternative PHP Cache]

=> sudo apt-get install libicu-dev [Install package for International Components for Unicode]

=> sudo apt-get install php5-suhosin [Install package for Advanced Protection System]

=> Add OR Edit below settings in php.ini [sudo gedit /etc/php5/apache2/php.ini] [sudo gedit /etc/php5/cli/php.ini]

-> suhosin.executor.include.whitelist=”phar”
-> date.timezone = UTC
-> short_open_tag = Off 
-> magic_quotes_gpc = Off 
-> register_globals = Off 
-> session.autostart = Off

=> sudo apt-get install libssl-doc [If not installed in System then install]

====== PROBLEM IN INSTALLATION THEN USE BELOW INSTRUCTIONS FOR THIS =======

=> sudo gedit /etc/apt/preferences

and insert the following lines:

Package: *

Pin: release a=precise*

Pin-Priority: 2012

Pin-Priority must be greater than 1000.

===========================================================================

Then you may downgrade the offending applications with:

=> sudo apt-get dist-upgrade [if u want]

Then you may install packages that complained about dependencies,

=> sudo apt-get install libssl-doc

=> sudo apt-get install libicu-dev

=> sudo apt-get install php5-intl

================== REMOVE THIS =================

Finally, you should remove the file you just created:

=> sudo rm /etc/apt/preferences

================================================

After you will Start your Symfony2 and see on URL: http://localhost/Symfony/web/config.php

Message : Your configuration looks good to run Symfony.