Question

I have a PHP process that takes a long time to run. I don’t want the AJAX process that calls it to wait for it to finish. When the PHP process finishes it will set a field in a database. There should be some kind of AJAX polling call to check on the database field periodically and set a message.

How do I set up a jQuery AJAX call to poll rather than wait? Does the PHP script have to do anything special?

Answer 1

It’s easier to have your server-side action, simply respond with a negative response until the value is ready and set up the client-side to repeatedly poll (with setTimeout()) until a positive response is received or a fixed number of failures is observed.

 var timer;
 var count = 0;
 function poll(url) {
      timer = setTimeout(function() {
          $.ajax({
              url: url,
              success: function(data) {
                  if (data.Status) {
                      ...do something...
                  }
                  else {
                     if (++count > 10) {
                       ...failure action...
                     }
                     else {
                         poll(url);
                     }
                  }
              ...other options...
           })
      },5000)
 }

Then on the server side use something that does (pseudocode) …

 if operation is not complete
     return serialize( { Status : false } )
 else
     data = ....
     data.Status = true
     return serialize(data)
 end