PHP的功能已经实现，却总是报错
代码的目的是实现图片上传到指定目录，并且在mysql中记录图片路径。
现在目的已经实现，可是页面总是报错，
报错内容就是第二行：
<?phpif ($_GET['action'] == "save"){ //这行报错：Notice: Undefined index: action in D:\xampp\htdocs\upload.php on line 2include_once('MYDBconn.php');include_once('UPclass.php');$titles=$_POST['title'];$images=$uploadfile;if($titles == "")echo"<Script>window.alert('No title');history.back()</Script>";$sql="insert into product(title,pic) values('$titles','$images')";$result=mysql_query($sql,$conn);echo"<Script>window.alert('congratunations');location.href='upload.php'</Script>";}?><html><head><title>images transfer</title></head><body> <form method="post" action="?action=save" enctype="multipart/form-data"> <table border=0 cellspacing=0 cellpadding=0 align=center width="100%"> <tr> <td width=55 height=20 align="center"> </TD> <td height="16"> <table width="48%" height="93" border="0" cellpadding="0" cellspacing="0"> <tr> <td>titles：</td> <td><input name="title" type="text" id="title"></td> </tr> <tr> <td>Images: </td> <td><label> <input name="file" type="file" value="view" > <input type="hidden" name="MAX_FILE_SIZE" value="2000000"> </label></td> </tr> <tr> <td> </td> <td><input type="submit" value="click me to upload" name="upload"></td> </tr> </table> </td> </tr> </table></form></body></html>