ArgumentCountError 🐘 PHP

Fatal error: Uncaught ArgumentCountError: Too few arguments to function foo(), 1 passed and exactly 2 expected

A function was called with fewer arguments than it requires.

Seen on: PHP

Meaning

Since PHP 7.1 missing required arguments throw ArgumentCountError. Common after adding a parameter to a function or constructor without updating every caller — including dependency-injection containers.

Common causes

  • New required parameter added; old callers not updated
  • Constructor injection missing a dependency
  • Callback invoked with fewer arguments than it declares

⚡ Quick fix

  1. Update callers or give the new parameter a default value
  2. Register the missing dependency in your DI container
  3. Make callback parameters optional

Detailed fix by platform

PHP

  1. Search the codebase for the function name after changing a signature; PHPStan reports mismatched calls

How to diagnose

  1. Function — Name and expected count in the message
  2. Caller — The stack trace's next frame

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