Plesk PHP & Web Server Configuration

The Problem

Different sites on the same Plesk server often need different PHP versions or extensions, and getting the per-domain settings wrong causes cryptic 500 errors that look like code problems but aren't.

About this problem

Plesk lets every domain run its own PHP version and settings, which is powerful but means a site can silently be running the wrong version, missing an extension it needs, or hitting a php.ini limit that produces a 500 error with no obvious cause. People often assume a cryptic error is a code problem when it's actually a one-line PHP setting at the Plesk level.

This usually comes up after installing a plugin or CMS that needs a specific PHP version or extension the current domain settings don't provide.

What's Included

• Setting the correct PHP version and handler type per domain
• Enabling required PHP extensions
• Adjusting key php.ini values (memory, upload size, execution time) sensibly
• Confirming each affected site loads correctly afterwards

What's NOT Included

• Fixing bugs in your site's actual code
• Installing custom/compiled PHP extensions not available via Plesk
• Web server config changes outside what Plesk exposes

How It Works

1. Check the current PHP version and handler (FPM application vs FPM served by Apache/Nginx) set on the affected domain.
2. Compare required PHP extensions against what's actually enabled for that domain.
3. Adjust key php.ini values — memory_limit, upload_max_filesize, max_execution_time — to match the application's real needs.
4. Apply the change and reload the affected service without disrupting other domains on the server.
5. Load the site and confirm the original error is gone with no new ones introduced.

In practice: you buy the service, send over whatever access or details the job needs, I investigate and do the work, and you confirm it's resolved before we call it done.

Frequently Asked Questions

Can different websites on the same Plesk server use different PHP versions?

Yes, that's one of Plesk's core features — each domain can be set to its own PHP version and handler independently of the others.

Why does my site show a 500 error after a plugin update?

Often the plugin needs a newer PHP version or an extension that isn't enabled for that specific domain in Plesk, which produces a generic 500 rather than a clear message.

How do I increase the PHP upload limit in Plesk?

It's set per domain in the PHP settings panel (upload_max_filesize and post_max_size together) — both need raising, since the lower of the two is the actual limit.

Will changing PHP settings for one domain affect others?

No, Plesk's per-domain PHP configuration is isolated, so changes to one site's settings don't touch any other domain on the server.

Can I install a custom PHP extension not listed in Plesk?

Only extensions available through Plesk's own PHP packages can be enabled through the panel; compiling custom extensions requires server-level access outside Plesk's normal interface.

What PHP memory limit should I use?

It depends on the application — WordPress typically needs at least 256M, while some plugins or import tasks need more. The right value is set based on what the specific site actually requires, not a blanket default.