PHP trigger from webpage A to load content from database on webpage B

I am building a chat and all works fine.

When person A types a message in a textarea and clicks the SEND button of an HTML form, PHP sends it to the server.

<?php

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // collect textarea content
    // inserted (appended) to mySQL table.
    // collect chat content in mySQL table
    // display chat content in a <div> 
    }
?>

(I am not posting the PHP code because it's irrelevant to the problem)

Person B gets the message because of a javascript setInterval that triggers a function that grabs the chat content from the database via AJAX and then displays the chat content for person B in a div.

setInterval(refreshChat, 1000);
function refreshChat() {
    $.ajax({
        url: "http://eyesonpi.com/_/php/chat.php",
        type: "post",
        success: function(data) {
        $("#chatWindow").html(data);
        },
        error: function() {
        $("#chatWindow").prepend("Error");
        }
        });
    }

When I tried it on my iPhone, running IOS 10, the AJAX call fails. IOS 10 has a problem with AJAX. https://forums.developer.apple.com/thread/64526

I tried with plain Javascript (xmlHttpRequest) and with jQuery.

I tried the chat window of my hosting company from my iPhone and their chat works. I don't know where to begin with a workaround. How can person B get the message from person A without reloading the page? Any suggestions?

Thank you.