In the form bindings panel when a file filed is added, there are 9 extra bindings created.
Informtion about a file uploaded using a form is not contained in the POST array. another array, the FILES array is created with information such as:
the client file name: <?php echo((isset($_FILES["fileField"]))?"fileField":"") ?>
the file extesnsion: <?php echo((isset($_FILES["fileField"]))? preg_replace('/^.*\./', '', $_FILES["fileField"]["name"]) :"") ?>
and Mime type: <?php echo((isset($_FILES["fileField"]))?$_FILES["fileField"]["type"]:"") ?>
These bindings should be used when you need to know something about the file when the form is posted. For example to validate that a file was selected.
to get a better understanding, create a blank PHP page, and add only the form tag and a file field. then examine the bindings panel. Do this before adding the upload file server behavior.
Once you add the upload file server behavior, the forms bindings dont change, but two new binding groups are created "Uploaded files (fileField)" and "Uploaded Files Global Status". The Global Status one is only used for troubleshooting.
The Uploaded files (fileField) binding group contains information about the file after it has been uploaded to the server.
If you examine it closely there 12 initial variables, ranging from "Status Code" to "Server File Name" and "Debug info".
If you stick with just the defaults and only upload the image to one location, there are 9 other bindings named like "[FileName]: Server File Name"
When uploading only one copy of the file, these other 9 variables are not really important.
But if you are uploading more than one copy of the file, say creating a thumbnail, then another 9 variables will be created named like "thumbs/[FilesName]: Server File Name".
In this case those additional bindings are used to get unique information about each copy of the file that is created.
The thumbnail file may be created with a different file name, so to store the thumbnails file name in the database, you would want to use the "thumbs/[FilesName]: Server File Name" binding.
to get a better understanding of these variables, add the upload file server behavior to the page, and configure it to only upload one copy of the file, then examine the bindings panel.
Now edit the upload behavior and configure it to create a thumbnail as well, then examine the bindings panel again.