To install PHP and mod_php module for Apache you have to run

apt-get install libapache2-mod-php5 php5 php5-common php5-curl php5-dev //
php5-gd php-pear php5-imagick php5-imap php5-mcrypt php5-mhash php5-mysql //
php5-pspell php5-recode php5-sqlite php5-tidy php5-xmlrpc php5-xsl php-apc imagemagick

If you do not need ImageMagick you can remove imagemagick and php5-imagick form the list. I use them because PHP Imagick extension provides a nice object oriented API to ImageMagick library.

php5-pspell installs aspell for spell checking purposes, which installs aspell-en dictionary. If you need some other dictionaries for your PHP applications install them as well.

To check for available language dictionaries type:

apt-cache search aspell-

A need Croation dictionary so I have to install the croatian package:

apt-get install aspell-hr

Now it is time to restart the Apache server

invoke-rc.d apache2 restart

By default, Apache server files from the /var/www folder on your server (we will change this later). To check if PHP is installed, create a new file using nano:

nano /var/www/i.php

and inside enter:

<?php phpinfo();

Try to open http://YOUR-IP-ADDRESS/i.php with your browser and you should see a PHP Info page. Remove the i.php file since exposing information about your web server to everyone is not a good idea:

rm /var/www/i.php

If you view your sites response headers (you can us WebDeveloper Toolbar for Firefox) you will see something like this:

Date: Mon, 13 Apr 2009 15:45:03 GMT
Server: Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny2 with Suhosin-Patch
X-Powered-By: PHP/5.2.6-1+lenny2
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 10251
Keep-Alive: timeout=15, max=99
Connection: Keep-Alive
Content-Type: text/html

200 OK

While we got rid of the Server: exposing PHP version, we also want to remove X-Powered-By header.

Open /etc/php5/apache2/php.ini and change

expose_php = On

to

expose_php = Off

While you are in the php.ini file change magic_quotes_gpc = On to magic_quotes_gpc = Off. I don't know why but Debian still ships PHP with magic quotes set to On.

Reboot the Apache web server and check the response headers. Now you should see something like this:

Date: Mon, 13 Apr 2009 15:57:43 GMT
Server: Apache
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 9920
Keep-Alive: timeout=15, max=99
Connection: Keep-Alive
Content-Type: text/html

200 OK