Recently helped my colleague to add the missing mysqli_ping() function to PDO object in PHP. If anyone missed it, here it is:

<?php
class NPDO {
    private $pdo;
    private $params;

    public function __construct() {
        $this->params = func_get_args();
        $this->init();
    }

    public function __call($name, array $args) {
        return call_user_func_array(array($this->pdo, $name), $args);
    }

    // The ping() will try to reconnect once if connection lost.
    public function ping() {
        try {
            $this->pdo->query('SELECT 1');
        } catch (PDOException $e) {
            $this->init();  // Don't catch exception here, so that re-connect fail will throw exception
        }

        return true;
    }

    private function init() {
        $class = new ReflectionClass('PDO');
        $this->pdo = $class->newInstanceArgs($this->params);
    }
}
?>

Today written a PHP class for handling multiple HTTP calls asynchronously (current only supports GET, feel free to modify it to support POST and PUT). By saying asynchronous, it can do something like this:

<?php
    $caller = new HttpCaller();
    $id1 = $caller->prepare($url1);
    $id2 = $caller->prepare($url2);
    $id3 = $caller->prepare($url3);

    // Send all requests and return immediately
    $caller->makeCall();

    // Doing something else here (fetching data from DB, computing... all sorts of stuff

    // Now we need the result for $url2 call, block until $url2 call return, but no need to wait for $url1 or $url3
    $result = $caller->fetch($id2);
    // Do something with $result and maybe something else

    $result = $caller->fetch($id1);    // Need the result for $url1 call
    // Do something with $result and maybe something else

    $result = $caller->fetch($id3);
    // Do something with $result
?>

Implementation of HttpCaller:

<?php
    class HttpCaller {
        private $timeout;
        private $mutliCurl;
        private $resultCache = array();

        public function __construct($timeout = 9999) {
            $this->timeout = intval($timeout);
            $this->multiCurl = curl_multi_init();
        }

        public function __destruct() {
            curl_multi_close($this->multiCurl);
        }

        public function prepare($url) {
            $curl = curl_init($url);
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($curl, CURLOPT_TIMEOUT, $this->timeout);

            curl_multi_add_handle($this->multiCurl, $curl);

            return intval($curl);
        }

        public function makeCall() {
            do {
                $res = curl_multi_exec($this->multiCurl, $isRunning);
            } while ($res == CURLM_CALL_MULTI_PERFORM);
        }

        public function fetch($id) {
            if (isset($this->resultCache[$id])) {
                return $this->resultCache[$id];
            }

            do {
                if (curl_multi_select($this->multiCurl) != -1) {
                    do {
                        $res = curl_multi_exec($this->multiCurl, $active);
                    } while ($res == CURLM_CALL_MULTI_PERFORM);

                    $info = curl_multi_info_read($this->multiCurl);
                    if ($info) {
                        if (curl_errno($info["handle"]) !== 0) {
                            return false;
                        }
                        $tmp = intval($info["handle"]);
                        $this->resultCache[$tmp] = curl_multi_getcontent($info["handle"]);

                        if ($tmp === $id) {
                            return $this->resultCache[$id];
                        }
                    }
                }
            } while ($active && $res == CURLM_OK);
        }
    }
?>

Just come across a stupid piece of JS program today in some web site:

function preselectSS(what)
{
  if (what == 1) document.getElementById("selSS").selectedIndex = 0;
  else if (what == 2) document.getElementById("selSS").selectedIndex = 1;
  else if (what == 3) document.getElementById("selSS").selectedIndex = 2;
  else document.getElementById("selSS").selectedIndex = 3;
}

Isn’t it a lot nicer to write it as

function preselectSS(what) {
    document.getElementById("selSS").selectedIndex = (what > 0 && what <= 3) ? (what - 1) : 3;
}

The world is full of stupid programmers writing stupid programs.

Update: The same functionality is now provided by the Yahoo! YUI Get Utility.

The YUI connection manager use XMLHttpRequest to make remote call, hence calling cross domain URL is prohibited by the browser security model. This class is to solve this situation without the need to setup any server side proxy, while maintaining the same calling mechanism as the YUI connection manager.

Script source: http://rockstonesand.com/js/crossdomainmanager.js

Minified version: http://rockstonesand.com/js/crossdomainmanager_min.js

Usage: Same as YUI connection manager

Functions supported:

asyncRequest, isCallInProgress, abort

Example:
Client side:

<script src="http://rockstonesand.com/js/crossdomainmanager_min.js"></script>
<script>
// Same callback object definition as YUI connection manager
var callback = {
    success: function(obj) {
        var response = obj.responseText;
        // Do UI updates
    },
    failure: function(obj) {
    }
};
var txId = CrossDomainConnect.asyncRequest(
   "http://api.flickr.com/services/feeds/photos_public.gne?lang=en-us&format=json",
   callback,
   "jsoncallback");
</script>

Limitations:

• Only GET method is supported, as it uses script tag hack
• The target server side script must support an additional “callback” parameter for the connection manager to specify a callback function

Good framework for applying MVC design in Web Application.

http://yuiblog.com/blog/2007/09/13/bubbling-library-by-caridy/

Recently I was helping my colleague to fix a strange bug in his Javascript. The bug behave like this:

1. Open the web page in IE.
2. After everything are loaded (HTML, images, scripts, …), click on address bar and press enter
3. IE crashed

When I try to identify the bug, I’ve created a simple page that can reproduce the bug.

crash.html

<div id="panel"></div>
<a href="#" onclick="loadScript(); return false;">Load script</a>

<script>
    var n = 0;
    var callback = function() {
        n++;
        var panel = document.getElementById("panel");
        panel.innerHTML = "loadScript called " + n + " times.";
        var node = document.getElementById("testid");
        node.parentNode.removeChild(node);
    }

    var loadScript = function() {
        var node = document.createElement("script");
        node.src="crash.js";
        node.id = "testid";

        document.getElementsByTagName("head")[0].appendChild(node);
    }

    window.onload = loadScript;
</script>

crash.js

callback();

What the page does is to create a script node dynamically and insert into the document to load an external .js file. When the external “crash.js” is loaded, it calls a function to update the page content and remove the script node. IE will be crashed by either click on the address and hit enter button or just click on the link “Load script”.

The actual reason why IE crashes on this situation is unknown, but one thing can be sure is it only crashes if the same URL is being requested. If you try to append a dummy random query to the script src URL, IE is working fine.

I’ve also discovered another way, which I think is better in solving this problem. Simply use a setTimeout() function to wrap around the removeChild statement with timeout = 0.

setTimeout(function() {
    var node = document.getElementById("testid");
    node.parentNode.removeChild(node);
}, 0);

The problem will be gone by doing this.