PHP依赖倒置(Dependency Injection)代码实例

<?php
 
class container
{
    protected $setings = array();
 
    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);
 
        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;
    }
}

<?php
 
require 'container.php';
 
 
interface myinterface{}
class foo implements myinterface{}
class bar implements myinterface{}
class baz
{
    public function __construct(myinterface $foo)
    {
        $this->foo = $foo;
    }
}
 
$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);