In my application I want to send some alerts to the client. I want to send updates to client without a request similar to push server.
How can I do this?
The best way to handle notifications without a permanent connection is to use what people refer too as a heartbeat function.
A heartbeat function is a function/method that gets called on a interval repeatedly just like your heart beats in a constant rhythm.
setInterval(function () {
$.get("/heartbeat.php", null, function (response) {
// check the response from heartbeat.php for new notifications
});
}, 10000);
Note: The above example contains jQuery code $.get( ... ), the non-jQuery way would be to make your ajax call using XMLHttpRequest.
The above would call the php script every 10 seconds to check for new notifications. New notifications can be added such as using a table inside a database. For example having a notifications table and 3 (4 if you want a date) fields: a user identifier field, message field, and a 'read'/'sent' flag field.
New notifications would get added to the table, and when the heartbeat script is called it'll check the user identifier and flag fields for new messages; if any are found then respond back with the message and mark it as sent.