Pass uploaded file between PHP scripts
===

I've got a page where users can upload a HTML file for use as a theme. The HTML file has some checks performed on it before some options are displayed to the user. The user fills out the form in relation to the HTML file, and submits the form. However, due to the file in the temp folder being destroyed after the script has ended, I do not know how to get the HTML file once the form has been filled out and re-submitted short of making the user re-upload the file, which relies on them uploading the same file, and also makes them upload something twice, which is counter-intuitive and could be an issue with large files.  
Here is the code (cut down to make it easier to read/understand). The form submits to itself, so the same PHP file is used for both "steps".  

    if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    	// Form has been submitted
    	$files = $_FILES['file'];
    	<form method="POST">
    		/* Options about the uploaded HTML file are generated using PHP and displayed here */
    		<input type="submit">
    	</form>
    } else {
    	?>
    	<form method="POST" enctype="multipart/form-data">
    		<label for="file">Theme File(s)</label>
    		<input type="file" name="file[]" multiple="multiple">
    		<input type="submit">
    	</form>
    	<?php
    }
I tried using `<input type="file" name="file[]" multiple="multiple" value="<?php echo $files; ?> >`, but this did not work, and would also require the user to re-upload the files, which could be any issue if the files get too big.  
I was thinking there might be a way to pass the file internally, and have a check whether a file has been uploaded or passed to the script instead of `<input type="file" name="file[]" multiple="multiple">`, but I could not find a way to do that.  