please help (uploading images)

[Gladiator2043]

I am using the following code to upload an image.

1). can this code be made better?
2). how do I link the uploaded image to the user uploading the image. e.g. to bring it up later

<?php 

// In PHP earlier then 4.1.0, $HTTP_POST_FILES should be used instead of $_FILES 

if($_FILES['userfile']['name'] == '') { 
       echo 'You did not select a photo to upload'; 
       } 
elseif($_FILES['userfile']['size'] == 0) { 
   echo 'There appears to be a problem with the photo your are uploading'; 
       } 
elseif($_FILES['userfile']['size'] > $MAX_FILE_SIZE) { 
        echo 'The photo you selected is too large'; 
       } 
elseif(!getimagesize($_FILES['userfile']['tmp_name'])) { 
        echo 'The photo you selected is not a valid image file'; 
       } 
else { 
   $uploaddir = 'seller_images/'; // remember the trailing slash! 
   $uploadfile = $uploaddir. $_FILES['userfile']['name']; 
   if(move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) { 
       echo 'Upload file success!'; 
   } 
   else { 
       echo 'There was a problem uploading your file.<br>'; 
       print_r($_FILES); 
   } 
} 

?>

[Roger_Ramjet]

Q2. answer

You link them by recording the filename and the user in a database table. Use an INSERT query once you have successfully uploaded the file.

[Gladiator2043]

How do I prevent over writes in the folder if the file names are the same?
Is there a better way i can name the file uploaded ?

thanks