Summary

Add Apache Event MPM as a web server option alongside Prefork and ITK.

Rationale

Event MPM would provide significant benefits for shared hosting:

• Better concurrency: threads instead of fork — handles more simultaneous connections with less RAM
• Full HTTP/2 support: Prefork only supports HTTP/2 with serious limitations (no multiplexing). Event MPM provides full HTTP/2 support.
• Enforced security: mod_php is incompatible with Event MPM (threaded model). This means mod_php is disabled by design, eliminating the security risk of PHP running as www-data in shared hosting environments.
• Isolation via PHP-FPM: each user already has a dedicated PHP-FPM pool running under their own uid/gid. Event MPM + mod_proxy_fcgi + PHP-FPM provides the same isolation as ITK but without the per-request fork overhead.

Implementation should be trivial

The logic for this is largely already in ISPManager:

1. Similar to Prefork: Event MPM configuration is nearly identical to Prefork. The main difference is LoadModule mpm_event_module instead of LoadModule mpm_prefork_module and threading directives (ThreadsPerChild, MaxRequestWorkers).
2. ISPManager already disables incompatible PHP modes per MPM: When switching to ITK, ISPManager automatically disables "PHP FastCGI (Apache)" because it is incompatible with ITK. The exact same logic can be applied to Event MPM: disable mod_php (incompatible with threads) and keep FastCGI (Apache), CGI, and Nginx+PHP-FPM available.
3. Available PHP modes per MPM:

Testing

We manually enabled Event MPM on ISPManager Host (Ubuntu 24.04) and confirmed:

• Same performance as Prefork (~29ms TTFB on a benchmark PHP page)
• All PHP modes except mod_php work correctly (CGI, FastCGI Apache, Nginx+PHP-FPM)