When installing Laravel 4 on a fresh Ubuntu or Debian system, you’ll probably get this error message: “Laravel requires the Mcrypt PHP extension.”
To install the mcrypt php extension, do this:
sudo apt-get install php5-mcrypt
and restart the server
sudo service apache2 restart
By the way, this might be off-topic, but let’s be honest: Laravel is a wonderful thing, but the install instructions are .. well… totally incomplete. It’s impossible to install laravel without doing some additional things that are simply not documented. The official tutorial completely misses the installation of the necessary plugins, necessary mod_rewrite shit and necessary vhost actions.