title: how to send back acknowledge message to html by php
body: <p>I'm a beginner in HTML and PHP. I made an HTML file include a form that sends variables with POST format to a PHP file for process and validation. In addition this form sends a picture file.</p>
  
  <p>But really I confused that this PHP file how send back acknowledge for show to user.
  For more description I want design an HTML form that send values to PHP and finally show user "thank you message" if the image size and format is valid or show "unable to upload your image" in first html form. Is it possible??
  Regards...</p>