Showing pop up when internet connection is lost in php

Question

I have simple php mysql data running page. with bootstrap.

How can i display an error when connection is lost?

How about popping up and modal as connection is lost & also trying to get connection & as connection gets back the modal disappears.

I have following modal:

<div id="myModal2" class="modal fade" role="dialog"> <div class="modal-dialog"> 
    <div class="modal-content"> 
        <div class="modal-header"> 
            <button type="button" class="close" data-dismiss="modal"> x </button> 
            <h4 class="modal-title">ERROR</h4> 
        </div> 
        <div class="modal-body"> 
            <p>You have lost connection
                </br> Trying again...
            </p> 
        </div> 
     </div> 
</div>