WordPress is a PHP application. Every page request runs through the PHP interpreter on your server, and the version of PHP your host provides has a huge effect on how fast, how secure, and how stable your WordPress site is. The PHP version is one of the parts of the stack that site owners think about least, and one of the parts that hosts most often leave alone unless asked. This is a problem.
This article explains why the PHP version matters, how to check what yours is running, and how to upgrade without breaking your site.
How PHP releases work
PHP has a public release schedule. A new major version comes out roughly every November. Each version receives full support for two years, then security only support for a third year, then nothing. After that, no security patches will ever be released for that version, no matter what flaw is discovered.
That last bit matters. A WordPress site running on PHP 7.4, which has been past end of life for years, is running on software that will never receive another fix. If a critical vulnerability is found tomorrow, your site will have it, and no patch will be coming.
Why hosts leave old PHP versions running
Hosts are usually reluctant to force PHP upgrades because they do not want to break customer sites. Some shared hosts will email you, then email you again, then quietly leave the default unchanged for years. Some hosts make a new version available but require you to opt in via a control panel.
The cautious approach is reasonable but it leaves the responsibility on you to actually click the button. Many sites we audit are sitting on a PHP version their host quietly offered to upgrade a year ago.
The security cost of old PHP
PHP, like any software, has bugs. Some of those bugs are security relevant. When PHP releases a security update, it usually applies to the current and one or two prior major versions. Older versions stay vulnerable. Attackers know which versions are still in wide use, which vulnerabilities apply, and which scanners to point at sites running them.
Even worse, some WordPress security fixes themselves depend on language features that only exist in newer PHP versions. A patched WordPress on an ancient PHP version can quietly behave differently from the same patched WordPress on a current version, leaving gaps that the security team did not intend.
The performance cost
PHP has improved its performance significantly across recent versions. Real world WordPress benchmarks consistently show double digit percentage improvements moving from PHP 7 to PHP 8, and further gains across the 8.x series. For a content heavy site, that translates to faster page loads, lower server costs, and better Core Web Vitals scores.
If your site has felt sluggish despite a good host and a clean plugin list, the PHP version is one of the first things to check. Free speed is sitting there waiting to be claimed.
How to check your PHP version
The quickest way is from inside WordPress. Go to Tools, then Site Health, then the Info tab. Expand the Server section. The PHP version is listed there along with the database version, the web server, and a few other details.
If you do not have access to the dashboard, ask your host. They will be able to tell you which version is active and which versions are available for upgrade. Reputable hosts will publish their supported PHP versions on their site.
The compatibility check before upgrading
Upgrading PHP is not just clicking a button. Old themes and plugins can use functions that were removed in newer PHP versions, or behaviour that was tightened up, or patterns that now generate fatal errors instead of warnings. A blind upgrade can take a site down.
The safe pattern is to run a compatibility check first. The official PHP Compatibility Checker plugin can scan your active theme and plugins against a target PHP version and report potential problems. Even better, a developer can run the modern equivalent on the codebase directly.
Whatever the scan reports, the actual test is to apply the upgrade on a staging copy first. The staging environment lets you see real behaviour with real data, including the issues a static check might miss.
What to do when a plugin is not compatible
If the staging upgrade reveals that a plugin breaks on the new PHP version, you have three choices. Find an alternative plugin that supports the new version. Patch the offending plugin yourself if you have the development capacity. Or accept that the plugin is abandoned and either pay someone to maintain it for you or migrate off it entirely.
What you should not do is stay on the old PHP version to keep the plugin alive. That is letting the weakest link in your stack hold back everything else.
A practical schedule for PHP upgrades
The simplest rule is to be at most one major version behind the current PHP release. As of mid 2026, the current stable line is PHP 8.4, with 8.3 in security only support. Anything older than 8.3 should be on your action list. Anything from the 7.x series should be treated as urgent.
Plan to test and upgrade once a year, ideally in the first quarter when the latest release has settled. Most hosts make the upgrade a single click, but the testing matters more than the click.
Need a hand?
If you are not sure which PHP version your site is on, or if you have been putting off the upgrade because of fear of breaking something, Smart Coding can run a compatibility check, prepare a staging site, and walk you through the upgrade safely. Get in touch and we will get the foundation under your WordPress site current.
