PHP upgrades still break WordPress sites—but rarely where people expect. This guide covers the 2026 reality: where core stands, what typically fails, and a practical workflow so you can upgrade with less risk.
Reality check (2026)
- WordPress core is solid on PHP 8.3 and officially supported
- PHP 8.4 surfaces more warnings and deprecations, especially in plugins and vendor libraries
- Failures usually originate in third-party code, not core
What typically breaks
- Deprecated behavior removed in PHP 8.x
- Stricter typing exposing latent bugs
- Vendor libraries with nullable parameter changes or outdated signatures
Practical workflow
- Inventory critical plugins and themes
- Test upgrades in staging first
- Upgrade PHP incrementally where possible (e.g. 8.1 → 8.2 → 8.3)
- Keep a fast plugin-disable plan ready
Stay current
- Check the official compatibility matrix and release notes at make.wordpress.org/core
FAQ
Should I jump straight to PHP 8.4?
Prefer stepping through 8.2 and 8.3 first so you can isolate which version triggers breakage. Many issues appear only on 8.4.
WordPress admin is blank after the upgrade.
Follow debugging WordPress after a PHP upgrade: check Apache and PHP-FPM logs, then disable plugins (or use WP-CLI) to find the culprit.
Related
- Why PHP upgrades break WordPress — why upgrades break
- Debugging WordPress after a PHP upgrade — debugging flow
- Safer plugin updates on production WordPress — update discipline
- PHP CLI vs PHP-FPM version mismatches — when CLI and web differ