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.
![Welcome to My New Office]()
My first professional web development was at a small print shop where I sat in a windowless cubical all day. I suffered that boxed in environment for almost five years before I was able to find a remote job where I worked from home. The first...
![How to Create a Twitter Card]()
One of my favorite social APIs was the Open Graph API adopted by Facebook. Adding just a few META tags to each page allowed links to my article to be styled and presented the way I wanted them to, giving me a bit of control...
![Advanced CSS Printing – Using JavaScript Double-Click To Remove Unwanted DIVs]()
Like any good programmer, I'm constantly searching around the internet for ideas and articles that can help me improve my code. There are thousands of talented programmers out there so I stumble upon some great articles and code snippets that I like to print out...
![Create a Sprited Navigation Menu Using CSS and MooTools]()
CSS sprites are all the rage these days. And why shouldn't be? They're easy to implement, have great upside, and usually take little effort to create. Dave Shea wrote an epic CSS sprites navigation post titled CSS Sprites2 - It's JavaScript Time.
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.