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Path and URL Constants for ClassicPress Plugins

A consistent set of constants for paths and URLs can improve speed and efficiency in creating ClassicPress plugins. Learn how to leverage this technique to save time and get more work done faster.

When you’re developing plugins for ClassicPress, you will often be referring to various paths and URLs, both within your plugin and within the greater ecosystem. You might need the site’s admin url, maybe you need your plugin’s scripts or styles directory… there are a lot of paths and URLs that you may need.

ClassicPress Paths and URLs

To be clear, ClassicPress does have functions that will get most paths and URLs that you typically would use in a plugin. However, if you’re like me, you may have trouble remembering all the function names or the arguments they take… or whether they have a trailing slash. What’s more, my code auto-completer can handle some of them quickly, while others leave me tabbing around to get in the right spot. I wanted a better solution.

Custom Paths and URLs

I’ve created a consist set of constants for paths and URLs that I can easily use in any ClassicPress plugin. They are easy to remember, work great with auto-completers, and there’s no more wondering about trailing slashes. Moreover, I’m able to write code much more efficiently – and that’s a win in my book!

The way I implement these constants in my plugins is to put them all into /my-plugin/includes/constants.php and include that file immediately within my initialization function in my plugin. So, let’s check’em out!

Namespacing the Constants

You’ll see that these constants have been namespaced. This isn’t a requirement, but it is recommended to avoid your code from polluting the global space and causing collisions. Now, let’s cover a few gotchas before they, well, getchya.

Gotcha #1

If you need to check whether a namespaced constant is defined, you must prepend the namespace.

Gotcha #2

If you use the define() function to define a constant, it must be prepended with the namespace. However, if you use the const keyword to define your constant, then the namespace is prepended automatically. The following code block demonstrates both methods of defining a constant.

Be sure to note that the code block above would produce an error – you can’t define the same constant twice, after all. You must choose one method or the other. These lines were included together above simply so you could see the differences in close proximity. No matter which method was chosen, the result would be the following namespaced constant:


To define() or to const? That is the question.

If you can use the const keyword, go for it. It’s the more modern way to define constants and gives you access to some additional cool tricks. In most cases, the const keyword will work. But, not always.

If you need to use a function (or any PHP) to generate the value of the constant defined by the const keyword, you’ll get an error. This is because you can’t have “code” on the right-hand side of the equation when you’re using const. In those cases, you can simply fall back to the older define() method of defining constants. The following code block demonstrates both succeeding and failing code.

Wrapping Up

The idea of using constants for frequently used paths and URLs isn’t new, but, it is often overlooked. It’s actually quite easy to implement these constants and it can dramatically improve your efficiency in writing new ClassicPress plugins. Time saved is money saved – start saving today!

What do you think?

Do you like the idea of having a set of defined constants, or do you think it’s overkill? And how about namespaces… were they easy to understand in this context? Or are you scraping your brain up off the keyboard right now? I’d love to know your thoughts – let me know in the comments.

2 comments on “Path and URL Constants for ClassicPress Plugins”

  1. A commenter said:

    This is interesting. When I write plugins, I use composer for the namespace and autoloading. Then I create a class for my constants which I extend to classes that require them. OOP perks.

    • AUTHOR
      Code Potent replied:

      Hey Laurence,

      It’s great to hear how you’re doing it! By placing all the constants into a class, it can make a handy “config object” for dependency injection elsewhere in a plugin. This can also help with testing. I like it. I’ve always tended to keep my constants outside of a class (though under a namespace,) but, I think it’s been more out of habit than anything. Thanks for sharing your thoughts.

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