autoloader.php

<?php

require_once('config.php');

function loadClass($className)
{
    $fileName = '';
    $namespace = '';

    // Sets the include path as the "src" directory
    $includePath = __DIR__ . DIRECTORY_SEPARATOR . 'src';

    if(false !== strripos($className, '\\')){
        $className = str_replace('\\API','',$className);
        $lastNsPos = strripos($className, '\\');
        $namespace = substr($className, 0, $lastNsPos);
        $className = substr($className, $lastNsPos + 1);
        $fileName = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
    $fullFileName = $includePath . DIRECTORY_SEPARATOR . $fileName;

    if(file_exists($fullFileName)){
        require $fullFileName;
    }
    else{
        die('Class "' . $className . ':' . $fileName.'" does not exist.');
    }
}

spl_autoload_register('loadClass'); // Registers the autoloader