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PHP Traits

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Trait

Traits are a mechanism for code reuse in single inheritance languages such as PHP. A Trait is intended to reduce some limitations of single inheritance by enabling a developer to reuse sets of methods freely in several independent classes living in different class hierarchies.

Trait 是一种代码重用的机制，由于PHP语言本身并不像C++等语言一样支持类的多继承，PHP用trait来实现“多继承”。用户可以用Trait声明一个包含属性和方法的对象，类可以引入多个trait并继承其中的属性和方法，以此来实现多继承

Note

  • trait 对象不能实例化

Usage

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<?php

trait t
{
	public function helloWorld()
	{
		printf("Hello World\n");
	}
}

class c
{
	use t;
}

$c = new c;
$c->helloWorld();
?>

输出

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$ php helloWorld.php 
Hello World

用trait实现多继承

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<?php

trait t1
{
	public function helloWorld()
	{
		printf("Hello World\n");
	}
}

trait t2
{
	public function thankYou()
	{
		print("Thank you\n");
	}	
}

class c
{
	use t1, t2;
}

$c = new c;
$c->helloWorld();
$c->thankYou();
?>

输出

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$ php c.php
Hello World
Thank you

Precedence

An inherited member from a base class is overridden by a member inserted by a Trait. The precedence order is that members from the current class override Trait methods, which in turn override inherited methods.

子类的属性和方法 > trait的属性和方法 > 父类的属性和方法

Reference & Thanks