CodeIgniter 4 vs CodeIgniter 3 — a practical guide to CodeIgniter 4 vs 3 with clear examples you can reuse in real projects.
CodeIgniter Tutorial Series (4/74). Prefer one article? Read the complete CodeIgniter tutorial.
Short description
CodeIgniter 4 is the modern version: namespaces, PHP 8+, improved HTTP layer, filters, and a cleaner structure. CI3 is legacy — new projects should use CI4.
Quick comparison
CI3: older structure, PHP 5.6+, fewer modern tools
CI4: namespaces, services, filters, spark CLI, PHP 8+
Recommendation: learn and build with CodeIgniter 4