PHP Migration Knowledge Base PSR-0 Autoloading

The compatibility classes provided with these migration guides use PSR-0 for greater compatibility with legacy autoloaders. If the project uses the Zend Framework 1 autoloader, just drop the Compatibility folder into the lib directory of the project, or whichever folder contains the Zend library. Example:

lib/
├─ Compatibility/
├─ Zend/

If no autoloader exists, here is the suggested PSR-0 autoloader implementation from the FIG website:

function autoload($className)
{
    $className = ltrim($className, '\\');
    $fileName  = '';
    $namespace = '';
    if ($lastNsPos = strrpos($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';

    require $fileName;
}
spl_autoload_register('autoload');

Alternatively, if you only need to use the class in one or two places, you can forego the autoloader and require the file directly, provided that the folder is in the include_path ini setting:

require_once 'Compatibility/Php56.php';