I am lucky to get the new layout

I am lucky to get the new layout, originally uploaded by Terence Yim.

Though a little bit off topic, looks like it starts rolling out.

Adding ping() function to PDO

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);
    }
}
?>

Stupid programming

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.

Cross domain connection manager with same calling mechanism as YUI

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

Update 2: Since the domain I used to host the file is not longer exist, I just paste the JS at the end of the post.

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.

The Bubbling Technique & Custom Event in YUI

Good framework for applying MVC design in Web Application.

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

Javascript that crashes IE

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>