Why `mixed` Is the Worst Type in Your PHP Codebase (and How to Kill It)

mixed is the type Laravel docs use, PHPStan tolerates, and your codebase quietly accumulates. Five failure modes and the migration path.

domenica 24 maggio 2026 New tab

2,028 words~9 min read

Book: Decoupled PHP — Clean and Hexagonal Architecture for Applications That Outlive the Framework

Also by me: Thinking in Go (2-book series) — Complete Guide to Go Programming + Hexagonal Architecture in Go

My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools

Me: xgabriel.com | GitHub

A team I talked to last month had 1,400 mixed return types across their Laravel 11 codebase. PHPStan level 6 was green. Tests passed. A junior dev refactored one helper, and three controllers started returning HTTP 500s in staging. Nothing flagged it. Nothing could.

Why `mixed` Is the Worst Type in Your PHP Codebase (and How to Kill It)

Why `mixed` Is the Worst Type in Your PHP Codebase (and How to Kill It)

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Related reading

PHP 8.4 Asymmetric Visibility: 5 Patterns That Replace Constructors and Setters

PHP Fibers in Production: 4 Real Cases Where They Beat curl_multi and Queues

The WordPress Paradox: Why It’s Here to Stay (and How to Stop Ruining It)

How I Let an AI Refactor My Whole Codebase (Using Gemini 3.5)

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