PHP technical interviews: what to actually prepare for
About to go through interviews at 3 companies. Senior PHP developer role. What do strong companies actually test?
Not looking for “study SOLID principles” type advice. Want to know what the hard questions are.
Database query optimization is the most common technical topic at senior level: given a slow query, how would you optimize it. EXPLAIN output reading, index design for specific access patterns, N+1 identification.
System design at the component level: design a queue system for delayed notifications, how would you handle 10k concurrent users on a single server, what breaks when you scale from 1 to 10 servers.
Debugging scenarios are common in good companies. “Users see each other’s data randomly. Walk me through your investigation.” Tests systematic thinking more than knowledge.
Code review exercises: they show you a Laravel PR with 5-10 real issues (security, N+1, wrong abstraction, missing validation). You find and explain the issues. Tests experience more than theory.
Infrastructure questions come up for senior roles: how do you deploy with zero downtime, describe your backup strategy, what happens when Redis goes down in your queue setup.
Security: name 3 OWASP Top 10 vulnerabilities and how to prevent them in PHP. SQL injection with prepared statements, XSS in Blade, CSRF protection. Basic but you need to be concrete, not vague.
Worst interview I had: asked to implement a linked list from scratch in PHP. No whiteboard, live coding editor. Took 40 minutes. Company was not worth joining if that is what they think senior PHP work looks like.
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