Technically I do not think its possible but thought I would ask. I have a form that contains multiple image upload fields, in the description we ask that the images size be smaller than 1mb but most people simple do not know how to check this.

Typically people will load each of the 5 image fields with an image over 2mb and wonder why the page timed-out or is blank after a couple of minutes.

Can PHP or something check this before the form gets rolling, then warn them about the size or time it will take to load these images?

It is not possible to look at the file on the client's hard drive before it is uploaded (which you would need to do to determine the size).

The only solution I can think of is to use an uploading script that instead of timing out the page, will abort the upload if it takes too long and then warn the user that their image was probably too large. I do not know of any such scripts however.

Most sites don't worry about the timing out, and just check the file size AFTER it is uploaded.

Unless you create a custom activex or java upload utility it is not possible to know the size if the file before the actual upload is completed.

Reading the uploaded headers and binary data and stopping midway once a particular size is reached is also another option but complicated

Check out the GD libraries for PHP. Do a google search for 'php-gd'

This is totally possible. let the user upload the file, run a script nad if the file is > 1mb delete the file from the server and send the user to an error page saying "YOU EEEDIOT!"