PHP class autoloader implementation method_php skills

function __autoload($className){
 $dirs=explode('_',$className);
 $fileName=array_pop($dirs);
 //print_r($dirs);
 $filePath=$fileName;
 if(is_array($dirs) && (count($dirs) > 0)){
  //echo '\n---\n'; print_r($dirs);
  $dirPath='';
  foreach ($dirs as $dir){
   if($dir){
    $dirPath.=strtolower($dir).DIRECTORY_SEPARATOR;
   }
  }
  $filePath=$dirPath.$fileName.'.php';
 }else {
  if( file_exists('class_'.$fileName.'.php')){
   $filePath='class_'.$fileName.'.php';
  }else {
   if( file_exists($fileName.'.class.php')){
    $filePath=$fileName.'.class.php';
   } else {
    $filePath=$fileName.'.php';
   }
  } 
 }
 //var_dump($filePath);
 require $filePath;
}