Detailed explanation of reflection mechanism in PHP

PHP5 adds a new feature: Reflection. This feature enables PHP to reverse-engineer class, interface, function, method and extension. Through PHP code, you can get all the information of an object and interact with it.
What is reflection?
It refers to extending the analysis of PHP programs in the running state of PHP, and exporting or extracting detailed information about classes, methods, properties, parameters, etc., including comments. This function of dynamically obtaining information and dynamically calling methods of objects is called reflection API. Reflection is an API for manipulating meta-models in the object-oriented paradigm. It is very powerful and can help us build complex and scalable applications.
Its uses include: automatically loading plug-ins, automatically generating documents, and can even be used to expand the PHP language.
The php reflection api consists of several classes that help us access the metadata of the program or interact with related annotations. With the help of reflection, we can obtain the methods implemented by the class, create an instance of the class (different from creating with new), call a method (also different from the regular call), pass parameters, and dynamically call the static methods of the class.
Reflection API is PHP’s built-in oop technology extension, including some classes, exceptions and interfaces. Used together, they can be used to help us analyze other classes, interfaces, methods, properties, methods and extensions. These oop extensions are called reflection.
Through ReflectionClass, we can get the following information of the Person class:
1) Constants
2) Properties Property Names
3) Method Names static
4) Properties Static Properties
5) Namespace Namespace
6) Whether the Person class is final or abstract

Example

class Person {  
    /** 
     * For the sake of demonstration, we"re setting this private
     */ 
    private $_allowDynamicAttributes = false;
 
    /** type=primary_autoincrement */
    protected $id = 0;
 
    /** type=varchar length=255 null */
    protected $name;
 
    /** type=text null */
    protected $biography;
 
        public function getId()
        {
        	return $this->id;
        }
        public function setId($v)
        {
           	$this->id = $v;
        }
        public function getName()
        {
       		return $this->name;
        }
        public function setName($v)
        {
         	$this->name = $v;
        }
        public function getBiography()
        {
          	return $this->biography;
        }
        public function setBiography($v)
        {
         	$this->biography = $v;
        }
}

Next to reflect it, just pass the class name "Person" Just give it to ReflectionClass:

$class = new ReflectionClass('Person');//建立 Person这个类的反射类
$instance  = $class->newInstanceArgs($args);//相当于实例化Person 类

1) Get properties (Properties):

$properties = $class->getProperties();
foreach($properties as $property) {
    echo $property->getName()."\n";
}
// 输出:
// _allowDynamicAttributes
// id
// name
// biography

By default, ReflectionClass will get all properties, private and protected are also available. If you only want to get the private properties, you need to pass an additional parameter:
$private_properties = $class->getProperties(ReflectionProperty::IS_PRIVATE);
Available parameter list:
ReflectionProperty::IS_STATIC
ReflectionProperty::IS_PUBLIC
ReflectionProperty::IS_PROTECTED
ReflectionProperty::IS_PRIVATE
If you want to get both public and private properties, just write: ReflectionProperty::IS _PUBLIC | ReflectionProperty::IS_PROTECTED.
You can get the property name through $property->getName().

2) Get comments:

You can get the comments written to the property through getDocComment.

foreach($properties as $property) {
    if($property->isProtected()) {
        $docblock = $property->getDocComment();
        preg_match('/ type\=([a-z_]*) /', $property->getDocComment(), $matches);
        echo $matches[1]."\n";
    }
}
// Output:
// primary_autoincrement
// varchar
// text

3) Get the methods of the class

Get the methods (methods): Get all the methods of the class through getMethods().

4) Execution class method:

$instance->getBiography(); //执行Person 里的方法getBiography
//或者：
$ec=$class->getmethod('getName');  //获取Person 类中的getName方法
$ec->invoke($instance);       //执行getName 方法

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