Too Few Arguments to Function

Why This Happens

PHP 7.1+ throws ArgumentCountError when a function receives fewer arguments than its required parameters. This replaces the older warning. It happens when you forget an argument, when a function signature changes but call sites are not updated, or when using call_user_func with the wrong number of arguments.

The Problem

function sendEmail(string $to, string $subject, string $body): void {
    // ...
}
sendEmail('user@example.com', 'Hello'); // Missing $body argument

The Fix

function sendEmail(string $to, string $subject, string $body = ''): void {
    // ...
}
sendEmail('user@example.com', 'Hello'); // Works with default body
// Or provide all arguments:
sendEmail('user@example.com', 'Hello', 'Welcome aboard!');

Step-by-Step Fix

1. 1

   Check the function signature

   Look at the function definition to see how many parameters are required and what types they expect.

2. 2

   Fix the call site

   Add the missing arguments to the function call, providing appropriate values for each required parameter.

3. 3

   Add defaults if appropriate

   If an argument is often optional, add a default value to the parameter in the function definition.