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PHP Intermediate 150 views

Cannot Redeclare Function

A function with the same name has already been defined in the current scope.

Explanation

Cannot redeclare function error occurs when PHP encounters a function definition that conflicts with an already-existing function in the same scope. This commonly happens when a file is accidentally included or required twice, when using autoloading that loads the same file multiple times, or when a function is defined in both a file and a library. In Laravel, this can happen with duplicate route definitions or when service providers register the same bindings.

Common Causes

  • File included/required twice
  • Autoloader loading duplicate files
  • Composer autoload configuration error
  • Function defined in both file and library
  • Circular dependency in includes

Solution

Check for duplicate require/include statements in your code. Verify the autoloader isn't loading the same file twice. Use require_once or include_once instead of require or include if the file might be needed multiple times. Check composer.json autoload configuration for duplicate entries. For Laravel, clear configuration and route caches. If defining functions in included files, use namespaces to prevent conflicts.

Code Example 

// This causes the error - file included twice
require 'helpers.php';
require 'helpers.php'; // Cannot redeclare helper()

// Fix: use require_once
require_once 'helpers.php';
require_once 'helpers.php'; // No error

// Check for duplicate autoload entries in composer.json
{
    "autoload": {
        "files": [
            "app/helpers.php"
        ]
    }
}

// Use namespaces to avoid conflicts
namespace App\Helpers;
function helper() { /* ... */ }

Error Information

Language

php

Difficulty

Intermediate

Views

150

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