PHP settings are adjustable per site, so a heavy WooCommerce store and a small brochure site on the same account can have different settings.
Where to change them
Open the site in your panel and find its PHP settings.
The settings that matter
PHP version. Newer is faster and better supported. Stay on a version that still receives security updates. Before you change version, test on staging, because an old plugin can fail on a new PHP release.
Memory limit. How much memory a single PHP request may use. WordPress is usually fine at 256 MB. WooCommerce and page builders are happier at 512 MB. Raising this does not raise your plan's total memory, it only changes how much one request may take of it.
Upload max file size. Raise this if WordPress rejects an image or a plugin zip as too large. 64 MB is a comfortable value for most sites.
Max execution time. How long a single request may run. Raise it if a long import times out. Do not leave it high permanently, because a runaway request will then hold your resources for longer.
Post max size. Should be at least as large as your upload max file size, or large uploads will still fail.
Your plan is the real ceiling
Per-request limits sit inside your plan's total memory: 512 MB on Starter, 1.5 GB on Pro, 3 GB on Premium, 5 GB on Platinum. Setting a 512 MB per-request memory limit on Starter will not work, because the account only has 512 MB in total. If you keep hitting limits, the answer is a bigger plan, not a bigger number in a settings box.
OPcache
PHP's own code cache is on. You do not need to configure it.
After a change
Changes apply immediately. Clear the page cache if you want to see the effect straight away.
If you are not sure
Ask the AI assistant in your panel. It can see your site's current settings and your plan's limits, and tell you whether the value you want is sensible.
The assistant in your control panel can see your actual account and answer about your sites, your plan and your usage. For anything else, email [email protected] and a person will answer.