PHP interpreter modes

PHP as an Apache module (mod_php)

In this mode, mod_php is loaded directly into Apache, and every Apache process includes it. Best suited for small sites with low traffic.

Advantages:

• fastest script execution compared to other modes;
• simple setup — the server handles scripts on its own;
• a single php.ini configuration file applies to all scripts;
• PHP settings can be defined in the Apache config or via .htaccess.

Disadvantages:

• all scripts run under the web server's user account, so directories that need write access must be world-writable;
• when scripts spawn external processes (e.g. mailing), it's impossible to identify which user triggered them;
• script processing adds load to Apache and can slow down static file delivery;
• errors in scripts can bring down the entire web server.

PHP as CGI

In this mode, a separate php-cgi process is launched for every request. Works well for sites that are mostly static, since the interpreter is only loaded when needed — saving RAM. The trade-off is slower execution, as a new process must be started on each request.

Advantages:

• scripts run under the domain owner's user account;
• PHP can be configured individually for each user;
• lower memory usage compared to mod_php;
• script errors don't crash the web server.

Disadvantages:

• PHP-based authentication via Header() may not work correctly, as some server variables aren't passed to the PHP script.

PHP as FastCGI

FastCGI sits between mod_php and CGI — it combines the strengths of both and eliminates CGI's main drawback. A persistent handler process runs in memory, so there's no need to spawn a new process on every request. In terms of speed, FastCGI is comparable to mod_php. It's the best fit for high-traffic sites with a steady stream of requests.

Advantages:

• intermediate data is cached, so scripts aren't re-interpreted on every request — faster than CGI;
• scripts run under the domain owner's user account.

Disadvantages:

• the php-cgi process stays in memory after the first request.

LSPHP

LiteSpeed PHP (LSPHP) is implemented as the mod_lsapi module for Apache and is the most performant PHP execution option on servers running cPanel.

Advantages:

• faster PHP script processing;
• no 500 errors caused by php_flag and similar directives in .htaccess — useful when migrating from a host that ran mod_php;
• lower resource consumption;
• improved Opcode Cache efficiency.

Installing PHP modules

PHP modules can be installed through the ISPmanager control panel under the PHP section.

Running a PHP script from cron

To run a PHP script via the cron scheduler, specify the full path to the interpreter before the script path:

/usr/bin/php-cgi /(path)/script.php

The script can be located in any directory, including ones that aren't accessible via FTP.