Open terminal and Type the command :install it first with
sudo apt-get install tasksel
sudo tasksel
Now check if php is working :
$sudo vi /var/www/info.php
<?php
phpinfo();
?>
save and exit
restart apache2 ,
#sudo /etc/init.d/apache2 restart
Now open browser and type :
http://ip/info.php or http://localhost/info.php 
Php is installed.
To full manage your lamp Server database, install phpmyadmin
sudo apt-get install phpmyadmin
To login to phpmyadmin, open browser and type :
http://ip/phpmyadmin or http://localhost/phpmyadmin
