PHP怎么依赖注入(Dependency Injection)的代码实例

实现类：

 <?php
  
 class Container
 {
     protected $setings = array();//@郑州网建
  
     public function set($abstract, $concrete = null)
     {
         if ($concrete === null) {
             $concrete = $abstract;
         }
  
         $this->setings[$abstract] = $concrete;
     }
  
     public function get($abstract, $parameters = array())
     {
         if (!isset($this->setings[$abstract])) {
             return null;
         }
  
         return $this->build($this->setings[$abstract], $parameters);
     }
  
     public function build($concrete, $parameters)
     {
         if ($concrete instanceof Closure) {
             return $concrete($this, $parameters);
         }
  
         $reflector = new ReflectionClass($concrete);//@郑州网建
  
         if (!$reflector->isInstantiable()) {
             throw new Exception("Class {$concrete} is not instantiable");
         }
  
         $constructor = $reflector->getConstructor();
  
         if (is_null($constructor)) {
             return $reflector->newInstance();
         }
  
         $parameters = $constructor->getParameters();
         $dependencies = $this->getDependencies($parameters);
  
         return $reflector->newInstanceArgs($dependencies);
     }
  
     public function getDependencies($parameters)
     {
         $dependencies = array();
         foreach ($parameters as $parameter) {
             $dependency = $parameter->getClass();
             if ($dependency === null) {
                 if ($parameter->isDefaultValueAvailable()) {
                     $dependencies[] = $parameter->getDefaultValue();
                 } else {
                     throw new Exception("Can not be resolve class dependency {$parameter->name}");
                 }
             } else {
                 $dependencies[] = $this->get($dependency->name);
             }
         }
  
         return $dependencies;
     }
 }

实现实例：

 <?php
  
 require 'container.php';
  
  
 interface MyInterface{}
 class Foo implements MyInterface{}
 class Bar implements MyInterface{}
 class Baz
 {
     public function __construct(MyInterface $foo)
     {
         $this->foo = $foo;//@郑州网建
     }
 }
  
 $container = new Container();
 $container->set('Baz', 'Baz');
 $container->set('MyInterface', 'Foo');
 $baz = $container->get('Baz');
 print_r($baz);
 $container->set('MyInterface', 'Bar');
 $baz = $container->get('Baz');
 print_r($baz);