Check for Function and Class Existence Using PHP
When you've inherited a big website or you're working on a group website where you don't have quick access to communicate with the other developers, it's important to not assume that a custom function or class name has not already been defined. Here's how you can protect yourself:
The PHP
if(!function_exists('show_article')) {
function show_article($id) {
//code here
}
}
if(!class_exists('my_class')) {
class myclass {
//code here
}
}
Using this type of programming can also protect you in case a file gets accidentally included twice. If a file with a function definition were to be included twice, you'd get an ugly "redefined" error when the function is realistically only in one file.
![Creating Scrolling Parallax Effects with CSS]()
Introduction
For quite a long time now websites with the so called "parallax" effect have been really popular.
In case you have not heard of this effect, it basically includes different layers of images that are moving in different directions or with different speed. This leads to a...
![5 Ways that CSS and JavaScript Interact That You May Not Know About]()
CSS and JavaScript: the lines seemingly get blurred by each browser release. They have always done a very different job but in the end they are both front-end technologies so they need do need to work closely. We have our .js files and our .css, but...
![jQuery Countdown Plugin]()
You've probably been to sites like RapidShare and MegaUpload that allow you to download files but make you wait a specified number of seconds before giving you the download link. I've created a similar script but my script allows you to animate the CSS font-size...
![Page Visibility API]()
One event that's always been lacking within the document is a signal for when the user is looking at a given tab, or another tab. When does the user switch off our site to look at something else? When do they come back?
It seems a little redundant to check for class existence when you’re trying to create a new class. If the class does exist, then you want yours to be named something else so that it can be used. I would personally want an error in the example above, so I knew to rename the class.
It would make sense to check for the class before instantiating it, but to check for the class before creating it, seems like it could create some confusing situations.
Thanks for this cool idea. Sometime it really becomes hard to follow other developers of the team, so this idea will really help.