├── README.md
├── client
    ├── client.js
    └── index.html
└── server
    ├── data.txt
    └── server.php


/README.md:
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 1 | # php-long-polling
 2 | 
 3 | A very simple demonstration of long-polling with AJAX (jQuery) and PHP. Long-polling makes near "real-time"
 4 | applications possible. The client does not request new data every X seconds/minutes, the client gets new data
 5 | delivered when there is new data (push-notification style). This is an improved, cleaned and documented
 6 | fork of https://github.com/lincolnbrito/php-ajax-long-polling ! Big thanks, man.
 7 | 
 8 | ## What is long-polling (and short polling) ?
 9 | 
10 | #### Short-polling
11 | 
12 | Send a request to the server, get an instant answer. Do this every x seconds, minutes etc. to keep your application
13 | up-to-date. But: This costs a lot of requests.
14 | 
15 | #### Long-polling
16 | 
17 | Send a request to the server, keep the connection open, get an answer when there's "data" for you. This will cost you
18 | only one request (per user), but the request keeps a permanent connection between client and server up.
19 | 
20 | ## How to use
21 | 
22 | To test, simply change the URL in client/client.js to the location of your server.php file, for local testing
23 | `url: 'http://127.0.0.1/php-long-polling/server/server.php'` will do the job. Open the `client/index.html` to simulate
24 | the client.
25 | 
26 | While having the index.html opened in your browser, edit the data.txt on the server (and save it). You'll see index.html
27 | instantly (!) getting the new content. Voila!
28 | 
29 | You should get a good idea how everything works by looking into the code, I think it's self-explaining.
30 | 
31 | ## In a real-world application ...
32 | 
33 | This would work perfectly in a real-world application, BUT
34 | 
35 | 1. There are better tools for this, like node.js, which can handle MUCH more concurrent connections and serve
36 | data faster, with much less memory usage and afaik while using only ONE thread.
37 | 
38 | 2. Apache2 uses 18MB afaik per thread by default, so having a "permanent connection" with 100 clients will use a lot
39 | of memory. I'm currently experimenting with lighttpd, NGINX and appserver.io to find a better solution.
40 | 
41 | ## You like that ?
42 | 
43 | :) Then have a look at my blog [DEV METAL](http://www.dev-metal.com), at [my other repos](https://github.com/panique) or support this and other projects by renting a server at [DigitalOcean](https://www.digitalocean.com/?refcode=40d978532a20) or tip a coffee at BuyMeACoffee.com. Thanks! :)
44 | 
45 | <a href="https://www.buymeacoffee.com/panique" target="_blank"><img src="https://cdn.buymeacoffee.com/buttons/v2/default-yellow.png" alt="Buy Me A Coffee" style="height: 60px !important;width: 217px !important;" ></a>
46 | 


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/client/client.js:
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 1 | /**
 2 |  * AJAX long-polling
 3 |  *
 4 |  * 1. sends a request to the server (without a timestamp parameter)
 5 |  * 2. waits for an answer from server.php (which can take forever)
 6 |  * 3. if server.php responds (whenever), put data_from_file into #response
 7 |  * 4. and call the function again
 8 |  *
 9 |  * @param timestamp
10 |  */
11 | function getContent(timestamp)
12 | {
13 |     var queryString = {'timestamp' : timestamp};
14 | 
15 |     $.ajax(
16 |         {
17 |             type: 'GET',
18 |             url: 'http://127.0.0.1/php-long-polling/server/server.php',
19 |             data: queryString,
20 |             success: function(data){
21 |                 // put result data into "obj"
22 |                 var obj = jQuery.parseJSON(data);
23 |                 // put the data_from_file into #response
24 |                 $('#response').html(obj.data_from_file);
25 |                 // call the function again, this time with the timestamp we just got from server.php
26 |                 getContent(obj.timestamp);
27 |             }
28 |         }
29 |     );
30 | }
31 | 
32 | // initialize jQuery
33 | $(function() {
34 |     getContent();
35 | });
36 | 


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/client/index.html:
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 1 | <html>
 2 |     <head>
 3 |         <script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
 4 |         <script type="text/javascript" src="client.js"></script>
 5 |     </head>
 6 |     <body>
 7 |         <h1>Response from server:</h1>
 8 |         <div id="response"></div>
 9 |     </body>
10 | </html>
11 | 


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/server/data.txt:
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1 | This is demo data from file data.txt ! Change (and save the file) to see the changed content INSTANTLY on your site !
2 | 


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/server/server.php:
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 1 | <?php
 2 | 
 3 | /**
 4 |  * Server-side file.
 5 |  * This file is an infinitive loop. Seriously.
 6 |  * It gets the file data.txt's last-changed timestamp, checks if this is larger than the timestamp of the
 7 |  * AJAX-submitted timestamp (time of last ajax request), and if so, it sends back a JSON with the data from
 8 |  * data.txt (and a timestamp). If not, it waits for one seconds and then start the next while step.
 9 |  *
10 |  * Note: This returns a JSON, containing the content of data.txt and the timestamp of the last data.txt change.
11 |  * This timestamp is used by the client's JavaScript for the next request, so THIS server-side script here only
12 |  * serves new content after the last file change. Sounds weird, but try it out, you'll get into it really fast!
13 |  */
14 | 
15 | // set php runtime to unlimited
16 | set_time_limit(0);
17 | 
18 | // where does the data come from ? In real world this would be a SQL query or something
19 | $data_source_file = 'data.txt';
20 | 
21 | // main loop
22 | while (true) {
23 | 
24 |     // if ajax request has send a timestamp, then $last_ajax_call = timestamp, else $last_ajax_call = null
25 |     $last_ajax_call = isset($_GET['timestamp']) ? (int)$_GET['timestamp'] : null;
26 | 
27 |     // PHP caches file data, like requesting the size of a file, by default. clearstatcache() clears that cache
28 |     clearstatcache();
29 |     // get timestamp of when file has been changed the last time
30 |     $last_change_in_data_file = filemtime($data_source_file);
31 | 
32 |     // if no timestamp delivered via ajax or data.txt has been changed SINCE last ajax timestamp
33 |     if ($last_ajax_call == null || $last_change_in_data_file > $last_ajax_call) {
34 | 
35 |         // get content of data.txt
36 |         $data = file_get_contents($data_source_file);
37 | 
38 |         // put data.txt's content and timestamp of last data.txt change into array
39 |         $result = array(
40 |             'data_from_file' => $data,
41 |             'timestamp' => $last_change_in_data_file
42 |         );
43 | 
44 |         // encode to JSON, render the result (for AJAX)
45 |         $json = json_encode($result);
46 |         echo $json;
47 | 
48 |         // leave this loop step
49 |         break;
50 | 
51 |     } else {
52 |         // wait for 1 sec (not very sexy as this blocks the PHP/Apache process, but that's how it goes)
53 |         sleep( 1 );
54 |         continue;
55 |     }
56 | }
57 | 


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