Contao\ClassLoader::getClasses PHP Method

    public static function getClasses()
    {
        return self::$classes;
    }

 /**
  * Returns all children of a given class
  * @param $strNamespace
  *
  * @return array
  */
 public static function getChildClasses($strQualifiedClassName)
 {
     $arrOptions = array();
     foreach (array_keys(ClassLoader::getClasses()) as $strName) {
         if (in_array($strQualifiedClassName, static::getParentClasses($strName))) {
             $arrOptions[$strName] = $strName;
         }
     }
     asort($arrOptions);
     return $arrOptions;
 }