Checking for uploaded files with file_exists - php

Question

I have a form for uploading data into my database.The form has a number of input fields ranging form text,number,textarea and file(images).
When the form is submitted, i check if there are any images being uploaded and if so, check if the image being uploaded passes a series of checks( below maximum file size, correct extension etc), with the entire process in a try/catch block set to throw exceptions should any check fail.
My checks are as follows:
$upload=$_FILES['Upload']['tmp_name'];
if(isset($upload))
{
if(!empty($upload) && is_uploaded_file($upload))
{
//Checks file size,extension and uploads the file
}
else
{
//throw new Exception
}
}
else
{
//throw new Exception
}
However, when using the above, isset would return true, even when no files are being uploaded.Upon some googling and looking on stack overflow, specifically isset and !empty not passing through a check for uploaded files , where it is stated that isset will return true due to $_FILES being a superglobal, i looked around for a solution and eventually settles on file_exists() as a replacement for isset() in my code.
My rationale for using file_exists() is that file that are uploaded(submitted) will be stored in a temp directory during the upload process, and if i check for this temp directory, i would thus be able to ascertain if a file is really uploaded.
After replacing isset() with file_exists my code is now working fine, but i am wondering if this is the correct way to proceed, or if there are any other better alternatives.
I look forward to any opinions and/or advice.

Answer 1

$upload=$_FILES['Upload']['tmp_name'];
if($upload)
{}
This will give the file temp name or null.

Answer 2

I would use the error-code given by $_FILES:
if($_FILES['Upload']['error'] == UPLOAD_ERR_OK) {
//seems to have worked
}
There are even other error-codes you could check against, for example if the file was to big etc.