How to detect if a user uploaded a file larger than post_max_size?

Question

How should I go about handling http uploads that exceeds the post_max_size in a sane manner?

In my configuration post_max_size is a few MB

Answer 1

I liked @Matthew answer, but needed a version that checked for multiple upload files.

This was my solution:

function checkAttachmentsSize() {
    var total = 0;
    var count = 0;

    jQuery('input[type="file"]').each(
        function() {
            if (typeof this.files[0] != 'undefined') {
                total+= this.files[0].size;
                count++;
            }
        }   
    );

    var word = (count > 1) ? 's are' : ' is';
    if (total > (uploadMax * 1000 * 1000)) {
        alert("The attachment file" + word + " too large to upload.");
        return false;
    }

    return true;
}

And, for completeness, here's the binding of the function to the form being submitted:

jQuery(function($) {
    $("form").submit(
        function() {
            return checkAttachmentsSize();
        }   
    });
);

NOTE:
uploadMax is a variable that I set via php after calculating the maximum size of the allowable upload.