PHP advanced features-detailed examples of reflection

1. What is reflection?

It refers to extending the analysis of PHP programs in the PHP running state, exporting or extracting detailed information about classes, methods, properties, parameters, etc., including Comment . This function of dynamically obtaining information and dynamically calling methods of objects is called reflection API.
Reflection is an API for manipulating the metamodel in the Object-oriented paradigm. Its function is very powerful and can help us build complex and scalable applications.

2. The use of reflection

Its uses include: Automatically loadingplug-ins, automatically generating documents, and can even be used to expand the PHP language.

3. Specific application examples of reflection-taking an implementation example of the CI framework

The reflection function is very powerful, so how to use it specifically? What are the application scenarios? Take the CI_Upload class of the CI framework to illustrate. (After searching ReflectionClass globally, I only found that reflection is useful here.)

The core logic of this method is that the caller passes a $config array when instantiating CI_Upload, and all configurations in the array are stored in the method. Assign the value to the corresponding class member attribute (if the attribute has a corresponding set_* method, call the set_* method)

Method 1. Writing without reflection:

public function initialize(array $config = array(), $reset = TRUE){
    $reflection = new ReflectionClass($this);
...    #遍历config，如果存在set_方法调用set方法，没有则直接赋值
    foreach ($config as $key => $v) {        if (method_exists($this, 'set_' . $key)) {            $this->{'set_' . $key}($v);
        }else{            $this->$key =$v;
        }
    }
...

This method has disadvantages : It is impossible to determine whether all the keys in the config array are legal and whether they are member attributes of the class
The judgment can be achieved using reflection.
The benefit of reflection here is that it can determine whether a class has properties (hasProperty) and whether a class has methods (hasMethod).

Method 2. Implementation within the CI framework

D:\project\app\system\libraries\Upload.php/**
 * Initialize preferences
 *
 * @param   array   $config
 * @param   bool    $reset
 * @return  CI_Upload
 */public function initialize(array $config = array(), $reset = TRUE){
    $reflection = new ReflectionClass($this);
...    foreach ($config as $key => &$value)
    {        if ($key[0] !== '_' && $reflection->hasProperty($key))
        {            if ($reflection->hasMethod('set_'.$key))
            {                $this->{'set_'.$key}($value);
            }            else
            {                $this->$key = $value;
            }
        }
    }
...

4. Summary

Regarding reflection (whether it is a reflection class (ReflectionClass) or a reflection function ReflectionFunction, it is actually a class and a function (difference) just remember one thing: reflection class/function can obtain all information about the class, including:
- basic information of the class (class name, whether it is an abstract class, whether it can be instantiated, whether the class is final or abstract)
- Class methods, whether the method exists, method return value, method annotation, Method Names
- Class attributes, static attributes, constants
- Location namespace Namespace

If you have the above situation, you might as well use reflection to solve it:)

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