How to use Firebird with PHP5 on Ubuntu or Debian?

You just need to install interbase extension:

sudo apt-get install php5-interbase

Check the ini file localted at "/etc/php5/conf.d/interbase.ini" or "/etc/php5/mods-available/interbase.ini" if the comment character is a # (sharp) change to ; (semicolon) to avoid warnings.

On ubuntu 13.10 copy:
/etc/php5/conf.d/interbase.ini

To:
/etc/php5/mods-available/interbase.ini

Then, to enable the extension, run:
php5enmod interbase

Optionally you can restart or reload your server.

Here's a guide for some older versions as well. Most probably does not work anymore, but we're keeping it here for historic documentation reasons:

Step 1: If you can't install Firebird support for PHP5 from official repositories, edit your /etc/apt/sources.list file and add:

deb http://people.debian.org/~dexter php5 sarge
deb-src http://people.debian.org/~dexter php5 sarge

and then update:

# apt-get update

Step 2: Now, simply install the module:

# apt-get install php5.0-firebird

It will also offer to install Apache, PHP5 and all the related packages. When done, make sure you restart Apache:

/etc/init.d/apache2 start

Enjoy.