Need a general idea for how to communicate with server PHP script and return error information to client
<p>I have a form that the user needs to populate and then the form will be sent to a server.
After the user submits the form, if the server script found that the form is not correctly populated (i.e. the uploading file is too big), it should return error to the client side.</p>

<p>Now, my question is as follows:</p>

<p>How do I keep the user seeing the same page without transferring to a different page?
Because I don't want the user to waste time to reenter everything again. I just want the user to correct the wrong part.</p>
