Upload_File

Hi I am trying to make a form to provide option to user to upload a file on
a server.Here is the code for my upload.php. It checks all the conditions
etc.. . This code works fine on localhost , and file is uploaded
successfully. But when I use this script online on my server, it gives me
error. couldn't figure out what is error.
What I think is error in move_upload_file, but it isn't returning any error.
File permissions on upload folder are 755.



if((!empty($_FILES['uploaded_file'])) && ($_FILES['uploaded_file']['error']
== 0)){

 $ok = 0;
  $filename = basename($_FILES['uploaded_file']['name']);

  $ext = substr($filename, strrpos($filename, '.') + 1);

  if (($ext == "jpg" || "gif" || "png") && ($_FILES["uploaded_file"]["type"]
== "image/jpeg" || "image/gif" || "image/png") &&
($_FILES["uploaded_file"]["size"] < 2097152) ){

      $newname = 'upload/'.$filename;

      if (!file_exists($newname)) {

        if
((move_uploaded_file($_FILES['uploaded_file']['tmp_name'],$newname))) {
        $ok = "1";
          echo "It's done! The file has been saved as: ".$newname;
        } else {
          echo "Error: A problem occurred during file upload!";   //This one
executes when ever i try to upload file on server.
        }
      } else {
         echo "Error: File ".$_FILES["uploaded_file"]["name"]." already
exists";
      }
  } else {
    echo "Error: Only .jpg images under 2MB are accepted for upload";
  }
} else {
 echo "Error: No file uploaded";
}

       Thanks
Bilal Farooq Ahmad