Detailed explanation of common magic methods in php, detailed explanation of php magic_PHP tutorial

Detailed explanation of common magic methods in php, detailed explanation of php magic

PHP stipulates that methods starting with two underscores (__) are reserved as magic methods, so it is recommended that your function name should not start with __ unless it is to overload an existing magic method.

The magic methods in PHP are: __construct, __destruct, __call, __callStatic,__get, __set, __isset, __unset, __sleep, __wakeup, __toString, __set_state, __clone, __autoload

1. __get, __set

These two methods are designed for properties that are not declared in the class and their parent class
__get( $property ) This method will be triggered when an undefined property is called, and the parameter passed is the name of the property being accessed
__set( $property, $value ) When assigning a value to an undefined property, this method will be triggered. The parameters passed are the set property name and value
The non-declaration here includes attributes whose access control is protected and private (that is, attributes that do not have permission to access) when called using an object.

2. __isset, __unset

__isset( $property ) This method is called when the isset() function is called on an undefined property
__unset( $property ) This method is called when the unset() function is called on an undefined property
The same as the __get method and __set method, the undeclared here includes attributes whose access control is protected and private (that is, attributes without permission to access) when called using an object

3. __call

__call( $method, $arg_array ) This method is called when calling an undefined method
The undefined methods here include methods that do not have permission to access; if the method does not exist, go to the parent class to find the method. If it does not exist in the parent class, call the __call() method of this class. If this class If the __call() method does not exist in the parent class, go to the __call() method in the parent class

4.__autoload
__autoload function, which is automatically called when trying to use a class that has not yet been defined. By calling this function, the scripting engine has a last chance to load the required classes before PHP fails with an error.
If you want to define a global autoloading class, you must use the spl_autoload_register() method to register the processing class to the PHP standard library:

Copy code The code is as follows:

class Loader
{ 
static function autoload_class($class_name)
{ 
//Find the correct $class_name class and introduce it, if not, an exception will be thrown
} 
} 
/**
* Set the automatic loading of objects
* spl_autoload_register — Register given function as __autoload() implementation
*/ 
spl_autoload_register(array('Loader', 'autoload_class'));
$a = new Test();//Test is instantiated without require to achieve automatic loading. Many frameworks use this method to automatically load classes
?>

Note: Exceptions thrown in the __autoload function cannot be caught by the catch statement block and cause fatal errors, so they should be caught in the function itself.

5. __construct, __destruct

__construct constructor, this method is called when an object is created. The advantage of using this method compared to PHP4 is that the constructor can have a unique name, no matter what the name of the class it is in. In this way, you are changing When the name of the class is used, there is no need to change the name of the constructor
__destruct destructor method, PHP will call this method before the object is destroyed (that is, before it is cleared from memory). By default, PHP only releases the memory occupied by object properties and destroys object-related resources. The destructor allows you to execute arbitrary code to clear memory after using an object. When PHP decides that your script is no longer associated with the object, the destructor will be called.
Within a function's namespace, this occurs when the function returns.
For global variables, this happens at the end of the script.
If you want to explicitly destroy an object, you can assign any other value to the variable pointing to the object. Typically assign the variable to NULL or call unset.

6. __clone

Object assignment in PHP5 uses reference assignment. If you want to copy an object, you need to use the clone method. When calling this method, the object will automatically call the __clone magic method. If you need to perform some initialization operations when copying the object, This can be achieved in the __clone method.

7.__toString

__toString method is automatically called when converting an object into a string, such as when using echo to print the object.
If the class does not implement this method, the object cannot be printed through echo, otherwise it will display: Catchable fatal error: Object of class test could not be converted to string in
This method must return a string.
Prior to PHP 5.2.0, the __toString method only took effect when used in conjunction with echo() or print(). After PHP 5.2.0, it can take effect in any string environment (for example, through printf(), using the %s modifier), but cannot be used in non-string environments (such as using the %d modifier). From PHP 5.2.0, if an object that does not define the __toString method is converted to a string, an E_RECOVERABLE_ERROR error will be reported.

8, __sleep, __wakeup

__sleep is used when serializing
__wakeup is called during deserialization
serialize() checks whether there is a function with the magic name __sleep in the class. If so, the function will run before any serialization. It clears the object and should return an array containing the names of all variables in the object that should be serialized.
The purpose of using __sleep is to close any database connections the object may have, submit pending data, or perform similar cleanup tasks. Additionally, this function is useful if you have very large objects that do not need to be stored completely.
Conversely, unserialize() checks for the existence of a function with the magic name __wakeup. This function can reconstruct any resources the object may have, if present.
The purpose of using __wakeup is to reestablish any database connections that may have been lost during serialization and to handle other reinitialization tasks.

9. __set_state

This static method will be called when var_export() is called (valid since PHP 5.1.0).
The only parameter of this method is an array containing class properties arranged in the format of array('property' => value, …).

10. __invoke

When trying to call an object by calling a function, the __invoke method is automatically called.
Valid for PHP5.3.0 or above

11. __callStatic

It works similar to the __call() magic method, __callStatic() is to handle static method calls,
Valid for PHP5.3.0 or above
PHP does tighten the definition of the __callStatic() method; it must be public and must be declared static. Likewise, the __call() magic method must be defined as public, as must all other magic methods

http://www.bkjia.com/PHPjc/932473.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/932473.htmlTechArticleDetailed explanation of common magic methods in php. Detailed explanation of php magic. PHP requires that methods starting with two underscores (__) be retained. It is a magic method, so it is recommended that your function name should not start with __, unless...