New features of modern PHP trait overview

Why use Trait

The PHP language uses a typical single inheritance model, in which we first write a generic root class, implement basic functionality, then extend the root class, create more specific subclasses, and inherit the implementation directly from the parent class. This is called an inheritance hierarchy, and many programming languages use this pattern. Most of the time this typical inheritance model works well, but what if you want two unrelated PHP classes to behave like this?

Trait was born to solve this problem. Trait can inject a modular implementation into multiple unrelated classes to improve code reuse and conform to the dry (Don T Repeat yourself) principle. For example Laravel bottom user authentication related logic as well as the soft deletion realization and so on place all uses the trait to realize. Take Laravel AuthController as an example, where the number of logins, registrations, and logon failure attempts are implemented through trait:

How to create a trait

Creating a trait is very simple, similar to creating a class, except that the keyword is used instead of the trait class above ThrottlesLogin example:

We trait define a trait by declaration, and then we can define the properties and methods to use in this trait like a class.

In addition, trait supports nesting and grouping, which combines one or more trait (multiple, delimited) into a trait, such as AuthenticatesAndRegistersUsers this:

Using multiple trait may cause a naming conflict problem, and the above code gives the solution: using insteadof keywords, if and AuthenticatesUsers RegistersUsers in both definitions redirectPath and getGuard methods, you will AuthenticatesUsers get the corresponding method instead of RegistersUsers . You can also use as keywords to make individual names for methods, so you can avoid naming conflicts.

In addition, it may not be fully listed here, and trait also supports the definition of abstract methods and static methods, where the abstract method must be implemented in the class that uses it.

One thing to declare here is the precedence of the calling method: the invocation class >Trait> parent class (if any), the method can overwrite, but the property is not, if a property is defined in Trait, it is an error if the property is defined in the calling class.

How to use trait

Trait is also very simple to use, which has been shown very clearly, that is, the use of use keywords.

As you may have noticed, namespaces and trait use use keywords, except for the import location where namespaces are imported outside the definition of the class, and trait is imported in the definition body of the class.

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Note: P The HP interpreter copies the trait to the class's definition at compile time, but does not handle the incompatibilities introduced by the operation, and if trait assumes that there are specific properties or methods in the class, it is necessary to ensure that the class does have a corresponding property or method.