Cannot Redeclare Function

Why This Happens

PHP does not allow two functions with the same name in the same scope. This error typically occurs when a file containing function definitions is included multiple times via require or include, or when two different files define a function with the same name.

The Problem

// index.php
require 'helpers.php';
require 'helpers.php'; // Included twice

// helpers.php
function formatDate($date) {
    return $date->format('Y-m-d');
}

The Fix

// index.php
require_once 'helpers.php'; // Only included once

// helpers.php
function formatDate($date) {
    return $date->format('Y-m-d');
}

Step-by-Step Fix

1. 1

   Find both declarations

   The error message tells you the function name and where it was previously declared. Search your codebase for all declarations of that function.

2. 2

   Switch to require_once

   Replace require and include with require_once and include_once to prevent files from being loaded multiple times.

3. 3

   Use namespaces or classes

   Organize functions into namespaced classes or use Composer autoloading to avoid manual file inclusion entirely.