说明：Laravel中经常使用PHP的反射特性来设计代码，本文主要学习PHP的反射特性，来提高写代码时的设计质量。PHP提供一套检测class, interface, trait, property, method的两个工具包：Introspection Functions和Reflection API，类似于探针一样的东西来探测这些一等公民。本文先看下Introspection Functions的使用。
开发环境: Laravel5.3 + PHP7
Introspection Functions
Introspection Functions是用来操作object class的一些函数，PHP提供了大量的Introspection Functions来操作class, interface, trait, method, property:
class_exists()
interface_exists()
method_exists()
property_exists()
trait_exists()
class_alias()
get_class()
get_parent_class()
get_called_class()
get_class_methods()
get_class_vars()
get_object_vars()
is_subclass_of()
is_a()
class_exists()
Laravel源码中好多个地方使用到class_exists()方法来判断指定类是否存在，如\Illuminate\Database\Connection::isDoctrineAvailable()的源码：
public function isDoctrineAvailable() { return class_exists('Doctrine\DBAL\Connection'); // Doctrine\DBAL\Connection::class类是否存在，大小写不敏感 } 写个PHPUnit测试下(爆绿灯，说明是正确的，这里不截图了。后面所有Introspection的测试都放在IntrospectionTest这个单元测试里)：
namespace MyRightCapital\Container\Tests;class IntrospectionTest extends \PHPUnit_Framework_TestCase{ public function testClassExists() { // Arrange // Actual $class_exists = class_exists(TestClassExists::class); // Assert $this->assertTrue($class_exists); }}class TestClassExists{ } interface_exists()
interface_exists()是用来检查接口是否存在，写个PHPUnit测试下，爆绿灯：
namespace MyRightCapital\Container\Tests;class IntrospectionTest extends \PHPUnit_Framework_TestCase{ public function testInterfaceExists() { // Arrange // Actual $interface_exists = interface_exists(TestInterfaceExists::class); // Assert $this->assertTrue($interface_exists); }}interface TestInterfaceExists{ } method_exists()
检查类的方法(private,protected,public)是否存在于指定的类对象或类名中，Laravel中很多处用到了这个函数，如Application中的register()检查service provider中register是否存在，和bootProvider()中检查service provider中boot()方法是否存在：
public function register($provider, $options = [], $force = false){ ... if (method_exists($provider, 'register')) { $provider->register(); } ...}protected function bootProvider(ServiceProvider $provider){ if (method_exists($provider, 'boot')) { return $this->call([$provider, 'boot']); }} 这里写个PHPUnit测试下，爆绿灯：
public function testMethodExists() { // Arrange $test_class_exists = new TestClassExists(); // Actual $object_method_exists1 = method_exists($test_class_exists, 'testPrivateMethodExists'); $object_method_exists2 = method_exists($test_class_exists, 'testProtectedMethodExists'); $object_method_exists3 = method_exists($test_class_exists, 'testPublicMethodExists'); $classname_method_exists1 = method_exists(TestClassExists::class, 'testPrivateMethodExists'); $classname_method_exists2 = method_exists(TestClassExists::class, 'testProtectedMethodExists'); $classname_method_exists3 = method_exists(TestClassExists::class, 'testPublicMethodExists'); // Assert $this->assertTrue($object_method_exists1); $this->assertTrue($object_method_exists2); $this->assertTrue($object_method_exists3); $this->assertTrue($classname_method_exists1); $this->assertTrue($classname_method_exists2); $this->assertTrue($classname_method_exists3); } class TestClassExists { private function testPrivateMethodExists() { } protected function testProtectedMethodExists() { } public function testPublicMethodExists() { } } property_exists()
检查该属性(private, protected, public)是否存在于类对象或类名中，Laravel很多地方用到了该函数，如\Illuminate\Foundation\Auth\RedirectsUsers::redirectPath()源码：
public function redirectPath() { return property_exists($this, 'redirectTo') ? $this->redirectTo : '/home'; } 写个PHPUnit测试下该函数，爆绿灯：
// class IntrospectionTest public function testPropertyExists() { // Arrange $test_class_exists = new TestClassExists(); // Actual $private_property1 = property_exists($test_class_exists, 'testPrivatePropertyExists'); $private_property2 = property_exists(TestClassExists::class, 'testPrivatePropertyExists'); $protected_property1 = property_exists($test_class_exists, 'testProtectedPropertyExists'); $protected_property2 = property_exists(TestClassExists::class, 'testProtectedPropertyExists'); $public_property1 = property_exists($test_class_exists, 'testPublicPropertyExists'); $public_property2 = property_exists(TestClassExists::class, 'testPublicPropertyExists'); // Assert $this->assertTrue($private_property1); $this->assertTrue($private_property2); $this->assertTrue($protected_property1); $this->assertTrue($protected_property2); $this->assertTrue($public_property1); $this->assertTrue($public_property2); } class TestClassExists { private $testPrivatePropertyExists; protected $testProtectedPropertyExists; public $testPublicPropertyExists; } trait_exists()
检查trait是否存在，写下PHPUnit测试，爆绿灯：
// class IntrospectionTest public function testTraitExists() { // Arrange // Actual $test_trait_exists = trait_exists(TestTraitExists::class); // Assert $this->assertTrue($test_trait_exists); } trait TestTraitExists { } class_alias()
给指定类取别名，Laravel中只有一处使用了class_alias()，用来给config/app.php中$aliases[ ]注册别名，可看下，看下Laravel中如何使用的：
public function load($alias) { if (isset($this->aliases[$alias])) { return class_alias($this->aliases[$alias], $alias); } } 写个PHPUnit测试，爆绿灯：
public function testClassAlias() { // Arrange class_alias(TestClassExists::class, 'MyRightCapital\Container\Tests\AliasTestClassExists'); $test_class_exists = new TestClassExists(); // Actual $actual = new AliasTestClassExists(); //Assert $this->assertInstanceOf(TestClassExists::class, $actual); $this->assertInstanceOf(AliasTestClassExists::class, $test_class_exists); } get_class()
get_class()获取对象的类名，这个函数在Laravel中大量地方在用了，如Application::getProvider($provider)方法，是个很好用的方法：
public function getProvider($provider) { $name = is_string($provider) ? $provider : get_class($provider); return Arr::first($this->serviceProviders, function ($value) use ($name) { return $value instanceof $name; }); } 写个PHPUnit测试，爆绿灯：
public function testGetClass() { // Arrange $test_class_exists = new TestClassExists(); // Actual $class_name = get_class($test_class_exists); // Assert $this->assertSame(TestClassExists::class, $class_name); } get_parent_class()
get_parent_class()是用来获取类的父类名，目前Laravel中还没用到这个函数，传入的可以是子类对象或者子类名，写个PHPUnit测试下：
// namespace MyRightCapital\Container\Tests; // class IntrospectionTest extends \PHPUnit_Framework_TestCase public function testGetParentClass() { // Arrange $child_class = new ChildClass(); // Actual $parent_class1 = get_parent_class($child_class); $parent_class2 = get_parent_class(ChildClass::class); // Assert $this->assertSame(ParentClass::class, $parent_class1); $this->assertSame(ParentClass::class, $parent_class2); } class ChildClass extends ParentClass { } class ParentClass { } get_called_class()
get_called_class()获取后期静态绑定类即实际调用类的名称，Laravel中还没使用到该函数，不妨写个测试看下如何使用：
// namespace MyRightCapital\Container\Tests; // class IntrospectionTest extends \PHPUnit_Framework_TestCase public function testGetCalledClass() { // Arrange $child_class = new ChildClass(); $parent_class = new ParentClass(); // Actual $child_called_class = $child_class->testGetCalledClass(); $parent_called_class = $parent_class->testGetCalledClass(); // Assert $this->assertSame(ChildClass::class, $child_called_class); $this->assertSame(ParentClass::class, $parent_called_class); } class ChildClass extends ParentClass { } class ParentClass { public function testGetCalledClass() { return get_called_class(); } } get_class_methods()
get_class_methods()用来获取类的方法名组成一个数组(测试只能是public)，Laravel只有一处用到了该方法\Illuminate\Database\Eloquent\Model::cacheMutatedAttributes() :line 3397,这里写个PHPUnit测试，爆绿灯：
public function testGetClassMethod() { // Arrange $get_class_methods1 = get_class_methods(ChildClass::class); $get_class_methods2 = get_class_methods(new ChildClass()); // Actual // Assert $this->assertFalse(in_array('testPrivateGetClassMethod', $get_class_methods1, true)); $this->assertFalse(in_array('testPrivateGetClassMethod', $get_class_methods2, true)); $this->assertFalse(in_array('testProtectedGetClassMethod', $get_class_methods1, true)); $this->assertFalse(in_array('testProtectedGetClassMethod', $get_class_methods2, true)); $this->assertTrue(in_array('testPublicGetClassMethod', $get_class_methods1, true)); $this->assertTrue(in_array('testPublicGetClassMethod', $get_class_methods2, true)); $this->assertTrue(in_array('testGetCalledClass', $get_class_methods1, true)); $this->assertTrue(in_array('testGetCalledClass', $get_class_methods2, true)); } class ChildClass extends ParentClass { private function testPrivateGetClassMethod() { } protected function testProtectedGetClassMethod() { } public function testPublicGetClassMethod() { } } get_class_vars()
get_class_vars()只会读取类的public属性组成一个数组，类似于get_class_methods()，若属性没有默认值就为null，目前Laravel中还未使用，看下PHPUnit测试：
public function testGetClassVars() { // Arrange // Actual $class_vars = get_class_vars(ChildClass::class); // Assert $this->assertArrayNotHasKey('privateNoDefaultVar', $class_vars); $this->assertArrayNotHasKey('privateDefaultVar', $class_vars); $this->assertArrayNotHasKey('protectedNoDefaultVar', $class_vars); $this->assertArrayNotHasKey('protectedDefaultVar', $class_vars); $this->assertEmpty($class_vars['publicNoDefaultVar']); $this->assertEquals('public_laravel', $class_vars['publicDefaultVar']); } class ChildClass extends ParentClass { private $privateNoDefaultVar; private $privateDefaultVar = 'private_laravel'; protected $protectedNoDefaultVar; protected $protectedDefaultVar = 'protected_laravel'; public $publicNoDefaultVar; public $publicDefaultVar = 'public_laravel'; } get_object_vars()
get_object_vars()只会读取对象的public属性组成一个数组，类似于get_class_vars(), get_class_methods()，且属性没有默认值就是null，Laravel中只有一处使用到\Illuminate\Mail\Jobs\HandleQueuedMessage::__sleep() :line 78，写个PHPUnit测试下，爆绿灯：
public function testGetObjectVars() { // Arrange $get_object_vars = new TestGetObjectVars(1, 2, 3); // Actual $object_vars = get_object_vars($get_object_vars); // Assert $this->assertArrayNotHasKey('x', $object_vars); $this->assertArrayNotHasKey('y', $object_vars); $this->assertEquals(3, $object_vars['z']); $this->assertArrayNotHasKey('dot1', $object_vars); $this->assertArrayNotHasKey('dot2', $object_vars); $this->assertArrayNotHasKey('circle1', $object_vars); $this->assertArrayNotHasKey('circle2', $object_vars); $this->assertEquals(10, $object_vars['line1']); $this->assertEmpty($object_vars['line2']); } class TestGetObjectVars { private $x; protected $y; public $z; private $dot1 = 10; private $dot2; protected $circle1 = 20; protected $circle2; public $line1 = 10; public $line2; public function __construct($x, $y, $z) { $this->x = $x; $this->y = $y; $this->z = $z; } } is_subclass_of()
is_subclass_of()用来判断给定类对象是否是另一给定类名的子类，Laravel中有用到，这里写下PHPUnit测试，爆绿灯：
public function testIsSubclassOf() { // Arrange $child_class = new ChildClass(); // Actual $is_subclass = is_subclass_of($child_class, ParentClass::class); // Assert $this->assertTrue($is_subclass); } is_a()
is_a()用来判定给定类对象是否是另一给定类名的对象或是子类，和is_subclass_of()有点类似，只是is_a()还可以判定是不是该类的对象，is_a()类似于instanceof操作符，Laravel中还没用到这个方法，这里写个PHPUnit测试，爆绿灯：
public function testIsA() { // Arrange $child_class = new ChildClass(); // Actual $is_object = is_a($child_class, ChildClass::class); $is_subclass = is_a($child_class, ParentClass::class); // Assert $this->assertTrue($is_object); $this->assertTrue($is_subclass); } 最后，给下整个PHPUnit的测试代码：
assertTrue($class_exists); } public function testInterfaceExists() { // Arrange // Actual $interface_exists = interface_exists(TestInterfaceExists::class); // Assert $this->assertTrue($interface_exists); } public function testMethodExists() { // Arrange $test_class_exists = new TestClassExists(); // Actual $object_method_exists1 = method_exists($test_class_exists, 'testPrivateMethodExists'); $object_method_exists2 = method_exists($test_class_exists, 'testProtectedMethodExists'); $object_method_exists3 = method_exists($test_class_exists, 'testPublicMethodExists'); $classname_method_exists1 = method_exists(TestClassExists::class, 'testPrivateMethodExists'); $classname_method_exists2 = method_exists(TestClassExists::class, 'testProtectedMethodExists'); $classname_method_exists3 = method_exists(TestClassExists::class, 'testPublicMethodExists'); // Assert $this->assertTrue($object_method_exists1); $this->assertTrue($object_method_exists2); $this->assertTrue($object_method_exists3); $this->assertTrue($classname_method_exists1); $this->assertTrue($classname_method_exists2); $this->assertTrue($classname_method_exists3); } public function testPropertyExists() { // Arrange $test_class_exists = new TestClassExists(); // Actual $private_property1 = property_exists($test_class_exists, 'testPrivatePropertyExists'); $private_property2 = property_exists(TestClassExists::class, 'testPrivatePropertyExists'); $protected_property1 = property_exists($test_class_exists, 'testProtectedPropertyExists'); $protected_property2 = property_exists(TestClassExists::class, 'testProtectedPropertyExists'); $public_property1 = property_exists($test_class_exists, 'testPublicPropertyExists'); $public_property2 = property_exists(TestClassExists::class, 'testPublicPropertyExists'); // Assert $this->assertTrue($private_property1); $this->assertTrue($private_property2); $this->assertTrue($protected_property1); $this->assertTrue($protected_property2); $this->assertTrue($public_property1); $this->assertTrue($public_property2); } public function testTraitExists() { // Arrange // Actual $test_trait_exists = trait_exists(TestTraitExists::class); // Assert $this->assertTrue($test_trait_exists); } public function testClassAlias() { // Arrange class_alias(TestClassExists::class, 'MyRightCapital\Container\Tests\AliasTestClassExists'); $test_class_exists = new TestClassExists(); // Actual $actual = new AliasTestClassExists(); //Assert $this->assertInstanceOf(TestClassExists::class, $actual); $this->assertInstanceOf(AliasTestClassExists::class, $test_class_exists); } public function testGetClass() { // Arrange $test_class_exists = new TestClassExists(); // Actual $class_name = get_class($test_class_exists); // Assert $this->assertSame(TestClassExists::class, $class_name); } public function testGetParentClass() { // Arrange $child_class = new ChildClass(); // Actual $parent_class1 = get_parent_class($child_class); $parent_class2 = get_parent_class(ChildClass::class); // Assert $this->assertSame(ParentClass::class, $parent_class1); $this->assertSame(ParentClass::class, $parent_class2); } public function testGetCalledClass() { // Arrange $child_class = new ChildClass(); $parent_class = new ParentClass(); // Actual $child_called_class = $child_class->testGetCalledClass(); $parent_called_class = $parent_class->testGetCalledClass(); // Assert $this->assertSame(ChildClass::class, $child_called_class); $this->assertSame(ParentClass::class, $parent_called_class); } public function testInArray() { $this->assertTrue(in_array('a', ['a', 'b', 1], true)); } public function testGetClassMethod() { // Arrange $get_class_methods1 = get_class_methods(ChildClass::class); $get_class_methods2 = get_class_methods(new ChildClass()); // Actual // Assert $this->assertFalse(in_array('testPrivateGetClassMethod', $get_class_methods1, true)); $this->assertFalse(in_array('testPrivateGetClassMethod', $get_class_methods2, true)); $this->assertFalse(in_array('testProtectedGetClassMethod', $get_class_methods1, true)); $this->assertFalse(in_array('testProtectedGetClassMethod', $get_class_methods2, true)); $this->assertTrue(in_array('testPublicGetClassMethod', $get_class_methods1, true)); $this->assertTrue(in_array('testPublicGetClassMethod', $get_class_methods2, true)); $this->assertTrue(in_array('testGetCalledClass', $get_class_methods1, true)); $this->assertTrue(in_array('testGetCalledClass', $get_class_methods2, true)); } public function testGetClassVars() { // Arrange // Actual $class_vars = get_class_vars(ChildClass::class); // Assert $this->assertArrayNotHasKey('privateNoDefaultVar', $class_vars); $this->assertArrayNotHasKey('privateDefaultVar', $class_vars); $this->assertArrayNotHasKey('protectedNoDefaultVar', $class_vars); $this->assertArrayNotHasKey('protectedDefaultVar', $class_vars); $this->assertEmpty($class_vars['publicNoDefaultVar']); $this->assertEquals('public_laravel', $class_vars['publicDefaultVar']); } public function testGetObjectVars() { // Arrange $get_object_vars = new TestGetObjectVars(1, 2, 3); // Actual $object_vars = get_object_vars($get_object_vars); // Assert $this->assertArrayNotHasKey('x', $object_vars); $this->assertArrayNotHasKey('y', $object_vars); $this->assertEquals(3, $object_vars['z']); $this->assertArrayNotHasKey('dot1', $object_vars); $this->assertArrayNotHasKey('dot2', $object_vars); $this->assertArrayNotHasKey('circle1', $object_vars); $this->assertArrayNotHasKey('circle2', $object_vars); $this->assertEquals(10, $object_vars['line1']); $this->assertEmpty($object_vars['line2']); } public function testIsSubclassOf() { // Arrange $child_class = new ChildClass(); // Actual $is_subclass = is_subclass_of($child_class, ParentClass::class); // Assert $this->assertTrue($is_subclass); } public function testIsA() { // Arrange $child_class = new ChildClass(); // Actual $is_object = is_a($child_class, ChildClass::class); $is_subclass = is_a($child_class, ParentClass::class); // Assert $this->assertTrue($is_object); $this->assertTrue($is_subclass); }}class TestGetObjectVars{ private $x; protected $y; public $z; private $dot1 = 10; private $dot2; protected $circle1 = 20; protected $circle2; public $line1 = 10; public $line2; public function __construct($x, $y, $z) { $this->x = $x; $this->y = $y; $this->z = $z; }}class ChildClass extends ParentClass{ private $privateNoDefaultVar; private $privateDefaultVar = 'private_laravel'; protected $protectedNoDefaultVar; protected $protectedDefaultVar = 'protected_laravel'; public $publicNoDefaultVar; public $publicDefaultVar = 'public_laravel'; private function testPrivateGetClassMethod() { } protected function testProtectedGetClassMethod() { } public function testPublicGetClassMethod() { }}class ParentClass{ public function testGetCalledClass() { return get_called_class(); }}class TestClassExists{ private $testPrivatePropertyExists; protected $testProtectedPropertyExists; public $testPublicPropertyExists; private function testPrivateMethodExists() { } protected function testProtectedMethodExists() { } public function testPublicMethodExists() { }}interface TestInterfaceExists{ }trait TestTraitExists{ } 
PHP不仅提供了检测class, interface, trait, property, method这些函数Introspection Functions，还提供了一整套的API即反射来检测class, interface, trait, property, method，这些API是好几个类组成的，提供了很多好用的方法。限于篇幅，下篇再聊下反射API。
总结：本文主要聊了下PHP提供的一套检测class, interface, trait, property, method的两个工具包：Introspection Functions和Reflection API，这里先聊到Introspection Functions。下篇再聊下Reflection API的使用，到时见。
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