Detailed explanation of trait singleton and calling instances in PHP

Trait单例

实例如下

<?php
trait singleton {    
    /**
     * private construct, generally defined by using class
     */
    //private function construct() {}
    
    public static function getInstance() {
        static $_instance = NULL;
        $class = CLASS;
        return $_instance ?: $_instance = new $class;
    }
    
    public function clone() {
        trigger_error(&#39;Cloning &#39;.CLASS.&#39; is not allowed.&#39;,E_USER_ERROR);
    }
    
    public function wakeup() {
        trigger_error(&#39;Unserializing &#39;.CLASS.&#39; is not allowed.&#39;,E_USER_ERROR);
    }
}
/**
* Example Usage
*/
class foo {
    use singleton;
    
    private function construct() {
        $this->name = &#39;foo&#39;;
    }
}
class bar {
    use singleton;
    
    private function construct() {
        $this->name = &#39;bar&#39;;
    }
}
$foo = foo::getInstance();
echo $foo->name;
$bar = bar::getInstance();
echo $bar->name;

调用trait方法

虽然不很明显，但是如果Trait的方法可以被定义为在普通类的静态方法，就可以被调用

实例如下

<?php 
trait Foo { 
    function bar() { 
        return &#39;baz&#39;; 
    } 
} 
echo Foo::bar(),"\\n"; 
?>

CLASS和TRAIT

CLASS 返回 use trait 的 class name，TRAIT返回 trait name

示例如下

<?php
trait TestTrait {
    public function testMethod() {
        echo "Class: " . CLASS . PHP_EOL;
        echo "Trait: " . TRAIT . PHP_EOL;
    }
}
class BaseClass {
    use TestTrait;
}
class TestClass extends BaseClass {
}
$t = new TestClass();
$t->testMethod();
//Class: BaseClass
//Trait: TestTrait

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