Introduction to reflection of handwritten PHP API framework (3)

In the previous article "Handwritten PHP API Framework: Installation and Use of Composer (2)" we introduced the installation and use of Composer. In this article we will introduce the concept of reflection.

Reflection, intuitive understanding is to find the departure place and source based on the arrival place. Reflection refers to extending the analysis of PHP programs in the running state of PHP, exporting or proposing detailed information about classes, methods, properties, parameters, etc., including comments. This function of dynamically obtaining information and dynamically calling object methods is called reflection API.

Let’s take a look at a demo first:

<?php


function p($msg, $var)
{
    echo($msg.":".print_r($var, true)).PHP_EOL.PHP_EOL;
}


class Demo
{
    private $id;

    protected $name;

    public $skills = [];

    public function __construct($id, $name, $skills = [])
    {
        $this->id = $id;
        $this->name = $name;
        $this->skills = $skills;
    }

    public function getName()
    {
        return $this->name;
    }
    public function getSkill()
    {
        p(&#39;skill&#39;, $this->skills);
    }
}


$ref = new ReflectionClass(&#39;Demo&#39;);
if ($ref->isInstantiable()) {
    p(&#39;检查类是否可实例化isInstantiable&#39;, null);
}
$constructor = $ref->getConstructor();
p(&#39;获取构造函数getConstructor&#39;, $constructor);

$parameters = $constructor->getParameters();
foreach ($parameters as $param) {
    p(&#39;获取参数getParameters&#39;, $param);
}

if ($ref->hasProperty(&#39;name&#39;)) {
    $attr = $ref->getProperty(&#39;name&#39;);
    p(&#39;获取属性getProperty&#39;, $attr);
}

$attributes = $ref->getProperties();
foreach ($attributes as $row) {
    p(&#39;获取属性列表getProperties&#39;, $row->getName());
}

if ($ref->hasMethod(&#39;getSkill&#39;)) {
    $method = $ref->getMethod(&#39;getSkill&#39;);
    p(&#39;获取方法getMethod&#39;, $method);
}

$methods = $ref->getMethods();
foreach ($methods as $row) {
    p(&#39;获取方法列表getMethods&#39;, $row->getName());
}

$instance = $ref->newInstanceArgs([1, &#39;sai&#39;, [&#39;php&#39;, &#39;js&#39;]]);
p(&#39;newInstanceArgs&#39;, $instance);

Output:

➜  php git:(main) php reflect.php 

检查类是否可实例化isInstantiable:

获取构造函数getConstructor:ReflectionMethod Object
(
    [name] => __construct
    [class] => Demo
)


获取参数getParameters:ReflectionParameter Object
(
    [name] => id
)


获取参数getParameters:ReflectionParameter Object
(
    [name] => name
)


获取参数getParameters:ReflectionParameter Object
(
    [name] => skills
)


获取属性getProperty:ReflectionProperty Object
(
    [name] => name
    [class] => Demo
)


获取属性列表getProperties:id

获取属性列表getProperties:name

获取属性列表getProperties:skills

获取方法getMethod:ReflectionMethod Object
(
    [name] => getSkill
    [class] => Demo
)


获取方法列表getMethods:__construct

获取方法列表getMethods:getName

获取方法列表getMethods:getSkill

newInstanceArgs:Demo Object
(
    [id:Demo:private] => 1
    [name:protected] => sai
    [skills] => Array
        (
            [0] => php
            [1] => js
        )

)

The ReflectionClass class is used in the demo. Of course, the ReflectionClass class is not limited to these methods.

More methods

The ReflectionClass class has more methods:

##ReflectionClass::__constructInitialize ReflectionClass ClassReflectionClass::exportExport a classReflectionClass::getConstantGet the definition A constantReflectionClass::getConstantsGet a set of constantsReflectionClass::getConstructorGet the constructor of the classReflectionClass::getDefaultPropertiesGet the default propertiesReflectionClass::getDocCommentGet documentation commentsReflectionClass::getEndLineGet the line number of the last lineReflectionClass:: getExtensionGet the ReflectionExtension object of the extension based on the defined classReflectionClass::getExtensionNameGet the name of the extension where the defined class is locatedReflectionClass::getFileNameGet the file name of the definition classReflectionClass::getInterfaceNamesGet Interface nameReflectionClass::getInterfacesGet interfaceReflectionClass::getMethodGet the ReflectionMethod of a class method. ReflectionClass::getMethodsGet the array of methodsReflectionClass::getModifiersGet the class ModifiersReflectionClass::getNameGet the class nameReflectionClass::getNamespaceName Get the name of the namespaceReflectionClass::getParentClassGet the parent classReflectionClass::getPropertiesGet a set of propertiesReflectionClass::getPropertyGet the ReflectionProperty of a property of the classReflectionClass:: getReflectionConstantGets a ReflectionClassConstant for a class's constantReflectionClass::getReflectionConstantsGets class constantsReflectionClass::getShortNameGet the short nameReflectionClass::getStartLineGet the starting line numberReflectionClass::getStaticPropertiesGet static properties##ReflectionClass::getStaticPropertyValueReflectionClass::getTraitAliasesReflectionClass::getTraitNamesReflectionClass::getTraitsReflectionClass::hasConstantReflectionClass::hasMethodReflectionClass::hasPropertyReflectionClass::implementsInterfaceReflectionClass::inNamespaceReflectionClass::isAbstractReflectionClass::isAnonymousReflectionClass::isCloneable##ReflectionClass::isFinalChecks whether the class is declared finalReflectionClass::isInstanceCheck the instance of the classReflectionClass::isInstantiableCheck whether the class is instantiableReflectionClass::isInterfaceCheck whether the class is an interfaceReflectionClass::isInternalCheck whether the class is represented by The extension or core defines internally ReflectionClass::isIterableCheck whether this class is iterableReflectionClass::isIterateable Check whether it is iterable(iterateable)ReflectionClass::isSubclassOfCheck whether it is a subclassReflectionClass::isTraitReturns whether it is a traitReflectionClass::isUserDefinedChecks whether it is defined by the userReflectionClass::newInstanceCreates a new class instance from the specified parametersCreate a new class instance from the given parameters. Creates a new class instance without calling its constructorSet the value of a static propertyReturns the string representation of the ReflectionClass object.

Method	Description
Get the value of static properties
Returns an array of trait aliases
Returns An array of the names of traits used by this class
Returns an array of traits used by this class
Check whether the constant has been defined
Check whether the method has been defined
Check whether the property has been defined
Implementation of the interface
Check if it is in the namespace
Check if the class is abstract Class (abstract)
Check whether the class is an anonymous class
Returns whether a class can be copied
	##ReflectionClass::newInstanceArgs
	ReflectionClass::newInstanceWithoutConstructor
	ReflectionClass:: setStaticPropertyValue
	ReflectionClass::__toString
	In addition to the powerful ReflectionClass, there are also Reflection, ReflectionClassConstant, ReflectionMethod, ReflectionFunctionAbstract and so on. It is recommended to check the manual: PHP Reflection Practical Application of Reflection ##Reflection can be used for document and file generation. You can use it to scan the classes in the file and generate description documents one by one; Since reflection can detect the internal structure of the class, you can use it as a hook to implement the plug-in function; can be used as a dynamic proxy to dynamically generate and instantiate some classes and execution methods when the class name is unknown or uncertain; Dependency injection. For classes that inherit multiple times, we can explore the structure of the base class through multiple reflections, or use recursive reflection to instantiate all inherited classes. This is also the principle of PHP dependency injection. Advantages of Reflection Languages ​​that support reflection provide some runtime features that are difficult to implement in low-level languages . can avoid hard coding to a certain extent and provide flexibility and versatility. Can discover and modify the structure of the source code (such as code blocks, classes, methods, protocols, etc.) as a first-class object. You can calculate symbolic syntax strings at runtime just like source code statements (similar to JavaScript's eval() function), and then convert strings matching class or function into a call or reference to a class or function. A new language bytecode interpreter can be created to give programming constructs a new meaning or purpose. Disadvantages of reflection The learning cost is high. Reflection-oriented programming requires more advanced knowledge, including frameworks, relational mapping and object interaction, to utilize more general code execution Also because the concept and syntax of reflection are relatively abstract, Excessive abuse of reflection technology will make it difficult for others to read the code, which is not conducive to cooperation and communication Reflection improves the flexibility of the code while sacrificing a little bit of operating efficiency. There is a certain amount of consumption Reflection will also destroy the encapsulation of the class and expose methods or properties that should not be exposed In In daily development, we don’t actually use reflection much, so why bring it here? Firstly, we will use reflection later to implement the Ioc container. Secondly, reflection is also one of the core functions of PHP. It is very common in our popular frameworks, and it is necessary to understand it. This section is relatively independent, we will use it in subsequent chapters. Recommended learning: " PHP Video Tutorial"

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