Examples of code reuse using traits in PHP_PHP Tutorial

Examples of using traits to achieve code reuse in PHP

This article mainly introduces examples of using traits to achieve code reuse in PHP. This article explains the simple use and priority of traits. level issues, multiple Trait conflicts, as can be used to modify method access control, the use of Traits in Traits, etc. Friends who need it can refer to it

Traits are added after PHP5.4 to implement the code reuse mechanism. Traits are similar to classes, but they cannot be instantiated and do not need to be inherited. You only need to use the keyword use in the class to introduce them. Multiple Traits can be introduced, using ',' separated.

(1) Trait is easy to use

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trait A { public $var1 = 'test1'; public function test1() { echo 'trait A::test1()'; } }   trait B { public $var2 = 'test2'; public function test2() { echo 'trait B::test2()'; } }   class C { use A,B; }   $c = new C(); echo $c->var1; //test1 $c->test2(); //trait B::test2()

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trait A { public $var1 = 'test'; public function test() { echo 'A::test()'; } public function test1() { echo 'A::test1()'; } }   class B { public function test() { echo 'B::test()'; } public function test1() { echo 'B::test1()'; } } class C extends B{ use A; public function test() { echo 'c::test()'; } }   $c = new C(); $c->test(); //c::test() $c->test1(); //A::test1()

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trait A { public $var1 = 'test1'; public function test1() { echo 'trait A::test1()'; } } trait B { public $var2 = 'test2'; public function test2() { echo 'trait B::test2()'; } } class C { use A,B; } $c = new C(); echo $c->var1; //test1 $c->test2(); //trait B::test2()

　(2)Priority issue Trait will override inherited methods, and the current class will override Trait methods. 　?

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trait A { public $var1 = 'test'; public function test() { echo 'A::test()'; } public function test1() { echo 'A::test1()'; } } class B { public function test() { echo 'B::test()'; } public function test1() { echo 'B::test1()'; } } class C extends B{ use A; public function test() { echo 'c::test()'; } } $c = new C(); $c->test(); //c::test() $c->test1(); //A::test1()

(3) Multiple Trait conflict issues

If the conflict is not resolved, a fatal error will occur;

You can use insteadof to specify which method in the conflict to use;

You can use the as operator to rename one of the conflicting methods;

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trait A { public function test() { echo 'A::test()'; } }   trait B { public function test() { echo 'B::test()'; } }   class C { use A,B { B::test insteadof A; B::test as t; } }   $c = new C(); $c->test(); //B::test() $c->t(); //B::test() 可以用as另起名

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trait HelloWorld { public function sayHello () { echo 'Hello World!' ; } }   // 修改 sayHello 的访问控制 class A { use HelloWorld { sayHello as protected; } }   // 给方法一个改变了访问控制的别名 // 原版 sayHello 的访问控制则没有发生变化 class B { use HelloWorld { sayHello as private myPrivateHello ; } }   $b = new A(); $b->sayHello(); //Fatal error: Call to protected method A::sayHello() from context ''

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trait A { public function test1() { echo 'test1'; } }   trait B { public function test2() { echo 'test2'; } }   trait C { use A,B; }   class D { use C; }   $d = new D(); $d->test2(); //test2

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trait A { public function test() { echo 'A::test()'; } } trait B { public function test() { echo 'B::test()'; } } class C { use A,B { B::test instead of A; B::test as t; } } $c = new C(); $c->test(); //B::test() $c->t(); //B::test() can be renamed with as

(4) as can be used to modify method access control 　?

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trait HelloWorld { public function sayHello () { echo 'Hello World!' ; } } // Modify the access control of sayHello class A { use HelloWorld { sayHello as protected; } } //Give the method an alias that changes access control //The access control of the original sayHello has not changed class B { use HelloWorld { sayHello as private myPrivateHello ; } } $b = new A(); $b->sayHello(); //Fatal error: Call to protected method A::sayHello() from context ''

　(5) Use Trait in Trait 　?

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trait A { public function test1() { echo 'test1'; } } trait B { public function test2() { echo 'test2'; } } trait C { use A,B; } class D { use C; } $d = new D(); $d->test2(); //test2

　(6) Trait supports abstract methods and static methods. Static variables cannot be directly defined, but static variables can be referenced by trait methods.

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trait A { public function test1() { static $a = 0; $a ; echo $a; }   abstract public function test2(); //可定义抽象方法 }   class B { use A; public function test2() {   } }   $b = new B(); $b->test1(); //1 $b->test1(); //2

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trait A { public $test1; }   class B { use A; public $test2;

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trait A { public function test1() { static $a = 0; $a ; echo $a; } abstract public function test2(); //Definable abstract method } class B { use A; public function test2() { } } $b = new B(); $b->test1(); //1 $b->test1(); //2

　(7) Trait can define attributes, but attributes with the same name cannot be defined in classes 　?

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trait A { public $test1; } class B { use A; public $test2;

http://www.bkjia.com/PHPjc/1000095.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1000095.htmlTechArticle Examples of using traits to implement code reuse in PHP This article mainly introduces traits to implement code reuse in PHP Usage examples, this article explains the simple use of Trait, priority issues, multiple Traits...