PHP traits for code reuse

This article mainly introduces the example of code reuse using traits in PHP, this article describes the simple use of Trait, priority issues, multiple Trait conflicts, as can be used to modify method access control, and Trait usage in Trait, you can refer to PHP 5.4 and add traits to implement code reuse. Trait is similar to the class, but it cannot be instantiated. you do not need to inherit it. you only need to use the keyword use in the class to introduce it, multiple Traits can be introduced, separated by commas.

(1) simple use of Trait

<?php 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
Trait will overwrite the inherited method, and the current class will overwrite the Trait method.

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 conflicts
If the conflict is not resolved, a fatal error occurs;
Insteadof can be used to determine which method of conflict is used;
Use the as operator to name one of the conflicting methods;

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 () can be named by another name.

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

Trait HelloWorld {public function sayHello () {echo 'Hello World! ';}} // Modify the access control class A {use HelloWorld {sayHello as protected;} of sayHello ;}} // give the method an access control alias that has changed the access control // the access control of the original sayHello does not change 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

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, static methods, and cannot directly define static variables. However, static variables can be referenced by the trait method.

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 the same name attribute cannot be defined in the class.

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