Using namespaces it becomes very easy, because now it is possible to match the folder structure with the namespace structure. Following that standards it is possible to make use of different tools that handle autoload, without having to code a custom autoloader. I have to say that WordPress coding standards have different rules for naming files. So when writing code for WordPress core, developers have to follow WP rules, but when writing custom code it's a developer choice, but using PSR standard is easier to use already written tools 2.
One of the biggest issues when instantiating plugin classes in WordPress, is how to access them from various parts of the code. WordPress itself uses the global approach: variables are saved in global scope, making them accessible everywhere. Every WP developer types the word global thousands of times in their career.
This answer is already much too long to allow me to further explain why, but reading the first results in the SERP for "global variables evil" is a good starting point.
It's easy and pretty fine, but it forces to implement the pattern for every class we want to access. Moreover, a lot of times this approach puts on the way to fall in the god class issue, because developers make accessible a main class using this method, and then use it to access all other classes.
I already explained how bad a god class is, so the static instance approach is a good way to go when a plugin only needs to make accessible one or two classes. This doesn't mean that it can be used only for plugins having just a couple of classes, in fact, when the dependency injection principle is used properly, it is possible to create pretty complex applications without the need to make globally accessible a large number of objects.
However, sometimes plugins need to make accessible some classes, and in that case the static instance approach is overwhelming. Another possible approach is to use the registry pattern.
Using this class it is possible to store objects in the registry object by an id, so having access to a registry it's possible to have access to all the objects. Of course when an object is created for the first time it needs to be added to the registry. The example above makes clear that to be useful the registry needs to be globally accessible. A global variable for the sole registry is not very bad, however for non-global purists it is possible to implement the static instance approach for a registry, or maybe a function with a static variable:.
The first time the function is called it will instantiate the registry, on subsequent calls it will just return it. Another WordPress-specific method to make a class globally accessible is returning an object instance from a filter. Something like this:. Another pattern that can be used is the service locator pattern.
It's similar to the registry pattern, but service locators are passed to various classes using dependency injection. Main problem with this pattern is that it hides classes dependencies making code harder to maintain and read. No matter the method used to make registry or service locator globally accessible, objects have to be stored there, and before to be stored they need to be instantiated.
In complex applications, where there are quite a lot classes and many of them have several dependencies, instantiating classes requires a lot of code, so the possibility of bugs increases: code that doesn't exist can't have bugs.
In last years there appeared some PHP libraries that help PHP developers to easily instantiate and store instances of objects, automatically resolving their dependencies. This libraries are known as Dependency Injection Containers because they are capable of instantiating classes resolving dependencies and also to store objects and return them when needed, acting similarly to a registry object.
Usually, when using DI containers, developers have to setup the dependencies for every class of the application, and then the first time a class is needed in the code it is instantiated with proper dependencies and the same instance is returned again and again on subsequent requests. Some DI containers are also capable to automatically discover dependencies without configuration, but using PHP reflection.
I want to point out that for simple plugins, that involve only few classes and classes have not many dependencies, probably it doesn't worth to use DI containers: the static instance method or a global accessible registry are good solutions, but for complex plugins the benefit of a DI container becomes evident. Of course, even DI container objects have to be accessible to be used in the application and for that purpose it is possible to use one of the methods seen above, global variable, static instance variable, returning object via filter and so on.
To use DI container often means using 3rd party code. Nowadays, in PHP, when we need to use an external lib so not only DI containers, but any code that isn't part of the application , simply downloading it and putting it in our application folder is not considered a good practice. Even if we are the authors of that other piece of code.
Decoupling an application code from external dependencies is sign of better organization, better reliability and better sanity of the code. Far away to be mainstream in WP community as well, it's a tool that every PHP and WordPress developer should at least know, if not use.
This answer is already book-sized to allow further discussion, and also discussing Composer here is probably off topic, it was only mentioned for sake of completeness. For more information visit the Composer site and it's also worth giving a read to this minisite curated by Rarst. Disclaimer I don't use unit tests yet so many things on myplate and I hear that static can be less preferable for them. Do your research on this if you need to unit test it. If you want to call it when your functions.
You might want to consider speed and memory usage. I'm not aware of any, but I can imagine there are uncalled hooks in some cases. By creating your instance at that hook you might save some server resources. I know this is a couple years old, but meanwhile php 5.
Before closures, whenever passing a function as an argument to another function, we had to define the function in advance and pass its name as the argument:. With closures, an anonymous i. Generators were added to PHP 5. Generators provide an easy way to implement simple iterators. A generator allows to write code that uses foreach to iterate over a set of data without needing to build an array in memory.
A generator function is the same as a normal function, except that instead of returning once, it can yield as many times as it needs to in order to provide the values to be iterated over. Different argument type declarations were introduced in different versions of PHP: WordPress is already able to declare interfaces and arrays which it does not: I barely found one instance of a function declaring an array as parameter in core, and no interfaces , and will soon be able to declare callables added in PHP 5.
Return type declarations were added to PHP 7. Argument type declarations allow functions to declare of what specific type must an argument be. The validation is executed at call time, throwing an exception if the type of the argument is not the declared one. Return type declarations are the same concept, however, they specify the type of value that will be returned from the function.
Type declarations are useful to make the intent of the function easier to understand and to avoid runtime errors from receiving or returning an unexpected type. The argument type is declared before the argument variable name, and the return type is declared after the arguments, preceded by : :. Scalar argument type declarations have two options: coercive and strict. In coercive mode, if the wrong type is passed as a parameter, it will be converted to the right type.
For example, a function that is given an integer for a parameter that expects a string will get a variable of type string. In strict mode, only a variable of the exact type of declaration will be accepted. Coercive mode is the default. Starting from PHP 5. Starting from PHP 7. PHP 7.
The Null coalescing operator?? It returns its first operand if it exists and is not NULL; otherwise, it returns its second operand. These are the most important new features added to PHP spanning versions 5. Next, we analyze how we can make the most out of all these new features, and from recent trends in web development, to produce better software.
The PHP Standards Recommendations was created by a group of PHP developers from popular frameworks and libraries, attempting to establish conventions so that different projects can be integrated more seamlessly and different teams can work better with each other. The recommendations are not static: existing recommendations may be deprecated and newer ones created to take their place, and new ones are released on an ongoing basis.
Components make it possible to use the best features from a framework without being locked-in to the framework itself. For instance, Symfony has been released as a set of reusable PHP components that can be installed independently of the Symfony framework ; Laravel , another PHP framework, makes use of several Symfony components , and released its own set of reusable components that can be used by any PHP project.
Fortunately, our minds work in objects anyway! Just like in real life, in OOP an object is a combination of properties and methods. Think about this for some other real-life objects around you. As basic as this sounds, it is most of the key to understanding the incredible power of object-oriented programming. As odd as it may sound, the bulk of WordPress is written procedurally. So the core thing that procedural code lacks, and that OOP gives us, is the ability to usefully group our code into entities— objects — that we find it easier to think about.
For that, we need OOP. In most programming languages, PHP included, each object arises from a class. In OOP, you can think of a class as a blueprint for objects. Just like a house blueprint explains the properties and methods of a living house to be constructed from it—but is not itself a house—a class explains the properties and methods of any living object made from it, while not itself being one of those objects.
This is how we declare our class. Notice that the class name, Dog , starts with a capital letter: this is customary to better tell between classes and functions. The process by which this transition occurs is the new keyword. Is that starting to make sense? In PHP, we instantiate objects with the keyword new. The extension classes may have more functions and variables. They may also redefine functions and variables already defined in the base class.
Using this pattern you can organize all your functions inside a static class doesn't need to be instantiated and then you can call functions in any template like so:. Yes, you can use classes in a Wordpress theme. Just remember to instantiate an object from that class before calling its methods. For instance, let's assume we want to capsulate function1 inside a class named Class1 :.
Now in order to call the functions we need to instantiate an object from that class :. How are we doing? Please help us improve Stack Overflow. Take our short survey. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Can I create own PHP class in wordpress theme function? Ask Question. Asked 8 years, 7 months ago. Active 8 years, 7 months ago.
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