Validating file extensions

1

how can i use ereg to validate file extensions.

eg: .jpeg .jpg .gif .png .swf .zip

i have this code and i want to adapt it


function validateFile($thefile,$description = ''){
 $result = ereg ("^[A-Za-z0-9\ ]+$", $thefile );
  if ($result){
   return true;
  }else{
   $this->errors[] = $description;
   return false;
  }
}