PHP 8.4 and 8.5: what you need to know – and when to upgrade

PHP is speeding up. At the same time, WordPress, TYPO3 and Shopware are raising minimum requirements. If you run websites seriously, you plan upgrades before security or compatibility problems catch you off guard. Here’s the current state and my clear roadmap.

Which PHP versions matter right now?

Clear: if you still run 8.1 (or older), you are on thin ice. Active support is gone and security support is expiring.

Upgrade strategy: how to get to 8.5 without drama

• Move to 8.4 now as soon as your plugins/extensions are compatible.
• Test 8.5 early as soon as your host offers stable builds.
• Staging before production: no experiments on live.
• Read logs: PHP error log and webserver log.
• Plan for breaking changes in custom themes/plugins.

WordPress: what I check in practice

• Update all plugins/themes – outdated baggage goes.
• Test page builders (e.g. Elementor, WPBakery, Gutenberg blocks) on 8.4/8.5.
• Click through WooCommerce end-to-end: cart, checkout, payment plugins.
• Scan child themes for deprecated functions (raise error_reporting in staging).

Unmaintained plugins get replaced – I don’t wait until they blow up a shop.

TYPO3: less tolerance, more discipline

• Check whether your LTS officially supports 8.4/8.5.
• Update all extensions via Composer and test compatibility.
• No hacks in system extensions. If it breaks: migrate properly.
• With older LTS versions, a core upgrade is usually unavoidable.

Shopware 6: no staging, no go

• Marketplace and custom plugins often break on new PHP – I test each one.
• Rebuild assets, check caches (HTTP, Redis, Opcache).
• Test integrations (payment, ERP, shipping) in staging – not “it feels fine”.
• After go-live: enable monitoring (logs, uptime, checkout tracking).

What happens if you don’t upgrade?

• Security vulnerabilities – and they will be exploited.
• Plugins suddenly become incompatible.
• Performance degrades and server costs rise.
• No support from core/vendors.
• Hosts simply disable old PHP versions – then timing is no longer yours.

Worst case: your shop is down when you need revenue. Nobody wants that.

What is PHP – and why do I keep it up to date?

PHP is the server-side language behind WordPress, TYPO3 and Shopware. Your code runs on the server and outputs HTML to the browser. If the foundation is outdated, security and compatibility are the first things that break.

My reasons for regular upgrades:

• Security issues get fixed.
• Deprecated functions disappear – less technical debt.
• Better performance and more stable runtimes.
• New features reduce development time.
• Hosts retire old versions – I prefer to act, not react.

Bottom line: if you take your website seriously, you keep PHP current. Period.

My recommendation

• Today: run PHP 8.4 in production.
• By Q1/2026: move cleanly to PHP 8.5.
• Routine: review and update plugins/extensions monthly.
• Process: staging → testing → go-live with monitoring.

Conclusion: PHP upgrades are maintenance, not “nice to have”. If you postpone it, you pay later with outages and stress.