Cannot redeclare class: how to autoload a class if exists already in a folder?

How can I check if a class exists already in a folder then do not load this class again from another folder?

I have this folder structure for instance,

index.php
  code/
  local/

And I have these two identical classes in code/ and local/

from local/

class Article
{
    public function getArticle()
    {
        echo 'class from local';
    }
}

from core,

class Article
{
    public function getArticle()
    {
        echo 'class from core';
    }
}

So I need a script that can detects the class of Article in local/ - if it exits already in that folder than don't load the class again from core/ folder. Is it possible?

This is my autoload function in index.php for loading classes,

define ('WEBSITE_DOCROOT', str_replace('\\', '/', dirname(__FILE__)).'/');

function autoloadMultipleDirectory($class_name) 
{
    // List all the class directories in the array.
    $main_directories = array(
        'core/', 
        'local/'
    );

    // Set other vars and arrays.
    $sub_directories = array();

    // When you use namespace in a class, you get something like this when you auto load that class \foo\tidy.
    // So use explode to split the string and then get the last item in the exloded array.
    $parts = explode('\\', $class_name);

    // Set the class file name.
    $file_name = end($parts).'.php';


    // List any sub dirs in the main dirs above and store them in an array.
    foreach($main_directories as $path_directory)
    {
        $iterator = new RecursiveIteratorIterator
        (
            new RecursiveDirectoryIterator(WEBSITE_DOCROOT.$path_directory), // Must use absolute path to get the files when ajax is used.
            RecursiveIteratorIterator::SELF_FIRST
        );

        foreach ($iterator as $fileObject) 
        {
            if ($fileObject->isDir()) 
            {
                // Replace any backslash to '/'.
                $pathnameReplace = str_replace('\\', '/', $fileObject->getPathname());
                //print_r($pathnameReplace);

                // Explode the folder path.
                $array = explode("/",$pathnameReplace);

                // Get the actual folder.
                $folder = end($array);
                //print_r($folder);

                // Stop proccessing if the folder is a dot or double dots.
                if($folder === '.' || $folder === '..') {continue;} 
                //var_dump($fileObject->getPathname());

                // Must trim off the WEBSITE_DOCROOT. 
                $sub_directories[] = preg_replace('~.*?(?=core|local)~i', '', str_replace('\\', '/', $fileObject->getPathname())) .'/';
            }
        }
    }


    // Mearge the main dirs with any sub dirs in them.
    $merged_directories = array_merge($main_directories,$sub_directories);


    // Loop the merge array and include the classes in them.
    foreach($merged_directories as $path_directory)
    {
        if(file_exists(WEBSITE_DOCROOT.$path_directory.$file_name))
        {
            // There is no need to use include/require_once. Autoload is a fallback when the system can't find the class you are instantiating. 
            // If you've already included it once via an autoload then the system knows about it and won't run your autoload method again anyway. 
            // So, just use the regular include/require - they are faster.
            include WEBSITE_DOCROOT.$path_directory.$file_name;
        } 
    }
}

// Register all the classes.
spl_autoload_register('autoloadMultipleDirectory');
$article = new Article();
echo $article->getArticle();

of course I get this error,

Fatal error: Cannot redeclare class Article in C:\wamp\...\local\Article.php on line 3

class_exists seems to be the answer I should look into, but how can I use it with the function above, especially with spl_autoload_register. Or if you have any better ideas?

Okay, I misunderstood your question. This should do the trick.

<?php

function __autoload($class_name) {
  static $core = WEBSITE_DOCROOT . DIRECTORY_SEPARATOR . "core";
  static $local = WEBSITE_DOCROOT . DIRECTORY_SEPARATOR . "local";

  $file_name = strtr($class_name, "\\", DIRECTORY_SEPARATOR):
  $file_local = "{$local}{$file_name}.php";

  require is_file($file_local) ? $file_local : "{$core}{$file_name}.php";
}

---

This is easily solved by using namespaces.

Your core file goes to /Core/Article.php:

namespace Core;

class Article {}

Your local file goes to /Local/Article.php:

namespace Local;

class Article {}

And then use a very simple autoloader, e.g.:

function __autoload($class_name) {
  $file_name = strtr($class_name, "\\", DIRECTORY_SEPARATOR);
  require "/var/www{$file_name}.php";
}

PHP loads your classes on demand, there's no need to load the files up front!

If you want to use an article simply do:

<?php

$coreArticle = new \Core\Article();
$localArticle = new \Local\Article();