How to gracefully handle files that exceed PHP's `post_max_size`?

Question

I'm working on a PHP form that attaches a file to an email, and trying to gracefully handle cases where the uploaded file is too large.

I've learned that there are two settings in php.ini that affect the maxiumum size of a file upload: upload_max_filesize and post_max_size.

If a file's size exceeds upload_max_filesize, PHP returns the file's size as 0. That's fine; I can check for that.

But if it exceeds post_max_size, my script fails silently and goes back to the blank form.

Is there any way to catch this error?

Answer 1

From the documentation :

If the size of post data is greater than post_max_size, the $_POST and $_FILES superglobals are empty. This can be tracked in various ways, e.g. by passing the $_GET variable to the script processing the data, i.e. <form action="edit.php?processed=1">, and then checking if $_GET['processed'] is set.

So unfortunately, it doesn't look like PHP sends an error. And since it sends am empty $_POST array, that is why your script is going back to the blank form - it doesn't think it is a POST. (Quite a poor design decision IMHO)

This commenter also has an interesting idea.

It seems that a more elegant way is comparison between post_max_size and $_SERVER['CONTENT_LENGTH']. Please note that the latter includes not only size of uploaded file plus post data but also multipart sequences.