modphp

Mod_php is an Apache HTTP Server module that embeds the PHP interpreter into the web server. When enabled, PHP code within files with .php is executed by PHP inside the Apache process, rather than by a separate interpreter process.

Implementation and operation: The module is loaded as a dynamic shared object (for example libphp7.so) at server startup and configured to handle PHP requests. It is most compatible with the prefork multi-processing module (MPM) of Apache, but can be used with some threaded MPMs when PHP is built with thread safety. Because the PHP interpreter runs inside Apache worker processes, memory usage scales with concurrent requests; this can limit the total concurrent connections on busy sites.

Security and isolation: Since PHP runs in the web server process, a PHP crash or exploit can affect the entire server and all virtual hosts sharing the same Apache process. This has led system administrators to favor separate PHP runtimes (such as PHP-FPM) for isolation and performance on modern deployments.

Modern usage and alternatives: While mod_php remains widespread on older or simpler deployments, many setups now use PHP-FPM (FastCGI Process Manager) with Apache via proxy or a separate FastCGI handler. This allows per-site or per-tenant isolation and easier scaling, and it enables running multiple PHP versions concurrently. Some distributions still provide mod_php packages for convenience.