HTML入門 | HTML5 API | SSE(Server Sent Events)

if (typeof(EventSource) !== "undefined") {
    // Server Sent Events用のコード
} else {
    // Server Sent Eventsをサポートしないブラウザー向けの案内
}

if(typeof(EventSource) !== "undefined") {
    var source = new EventSource("/examples/media/sse.php");
    source.onmessage = function(event) { 
        document.getElementById("result").innerHTML += event.data + "<br>"; 
    };
}

<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
 
$time = date('r');
echo "data: The server time is: {$time}\n\n";
flush();
?>