Static Members & Methods

So far, we've only seen instance methods and instance variables. These are methods and variables that belong to an instance of a class. For example, if we have a User class, we can create many new instances of that user. However, there are cases where we don't need multiple instances and we want to create a method or variable that belongs to the class itself, not to an instance of the class. These are called static methods and static variables.

Let's create a new class called MathUtility and add a static property called $pi and a static method called add. We do this by just adding the static keyword before the property or method name:

class MathUtility
{
    public static $pi = 3.14159;

    public static function add(...$nums)
    {
        return array_sum($nums);
    }
}

Now we can access the static property and method without creating a new instance of the class:

echo MathUtility::$pi; // 3.14159

Notice the way that we access the static property. We use the class name followed by the scope resolution operator :: and then the property name. This is different than the arrow operator -> that we use to access instance properties and methods.

You can probably see the reason we made this property static. We don't need multiple instances of the MathUtility class. We only need one instance of the $pi property. We can access it from anywhere in our code without having to create a new instance of the class.

Let's try the static method:

echo MathUtility::add(1, 2, 3, 4, 5); // 15

Again, we use the class name followed by the scope resolution operator :: and then the method name. We don't need to create a new instance of the class to use the method.