Minimum space for the application files: 10 MBytes. Project specific picture files and data require additional space. For a usual project with 500 users, 1 GB should be sufficient.
PHP, minimum version 5.3.0.
The PHP configuration option safe_mode must have value off. You might ask your web host provider whether safe_mode is switched off on your server. This option does not exist anymore from PHP version 5.4.0.
The PHP library GD must be installed. This should be standard at most providers, but you might ask yours anyway.
The PHP extension JSON must be installed. This should be standard as well.
MySQL database, minimum version 4.1.
The MySQL database must support InnoDB. This should be standard, but better ask.
If using external web services, such as from Facebook and Google+, the PHP extension CURL must be enabled.
When simulating matches minute-by-minute, it is recommended to have a Cron job which can be executed every minute. Most of the web host providers offer such Cron jobs, however often for extra charge.
Your webhost provider should allow the operation of an online game. It is recommended to get a written approval from the provider.