PHP Magic Method

From PHP 5 onwards, classes in PHP can use the Magic method. The rules that begin with two underscores (__) are preserved as magic methods, so it is recommended that you do not start with the function name unless you are trying to reload the existing magic method.

1, __get, __set

These two methods are designed for properties that are not declared in the class and their parent class.

__get ($property) When an undefined property is called, this method is triggered, and the passed parameter is the property name that is accessed.

__set ($property, $value) when assigning a value to an undefined property, this method is triggered, and the passed parameter is the property name and value that is set.

There is no declaration here that the access control is a Proteced,private property (that is, a property without permission access) when using object invocation.

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.

As with the __get method and the __set method, there is no declaration here that the access control is a property of Proteced,private when using an object invocation (that is, a property that does not have permission to access).

3, __call

__call ($method, $arg _array) calls this method when an undefined method is called.

The undefined method here includes a method that does not have access, if the method does not exist in the parent class to find this method, if it does not exist in the parent class to call the __call () party of this class, if the __call () method does not exist in this class to find the __call () method in the parent class.

4, __autoload

The __autoload function, which is called automatically when trying to use a class that has not yet been defined. By calling this function, the scripting engine has the last chance to load the required classes before PHP fails.

If you are defining a global auto-load class, you must register the processing class with the PHP standard library using the Spl_autoload_register () method:

<?php
Class Loader   
{          
    static function Autoload_class ($class _name)        {          
    Look for the right $class_name class, and introduce, no then throw an exception          
     }         
}      

*  Set Object Auto-loading        
*  Spl_autoload_register-register given function as __autoload () implementation       
*/   
Spl_autoload_register (Array (' Loader ', ' Autoload_class '));   

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

5, __construct, __destruct

__construct constructs a method that calls this method when an object is created, and the advantage of using this method with respect to PHP4 is that the constructor can have a unique name, regardless of the name of the class in which it resides. So you don't need to change the name of the constructor when you change the name of the class.

__destruct destructor, PHP calls this method before the object is destroyed (that is, before it is purged from memory). By default, PHP simply frees the memory occupied by the object's properties and destroys the object-related resources, and the destructor allows you to execute arbitrary code to clear the memory after using an object. When PHP decides that your script is no longer related to the object, the destructor is called.

Within the namespace of a function, this occurs at the time of the function return. 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 that points to the object. You typically assign a variable to be on duty to null or call unset.

6, __clone

The object assignment in PHP 5 is to use a reference assignment, and if you want to copy an object then you need to use the Clone method, which is called by the object to automatically call the __clone magic method, if the object copy needs to perform some initialization operations, it can be implemented in the __clone method.

7, __tostring

The __tostring method is called automatically when an object is converted to a string, such as when using Echo to print an object.

If the class does not implement this method, the object cannot be printed through ECHO, otherwise it will be displayed: Catchable fatal Error:object of class test could not being converted to string in, this method must return a character String.

Before PHP 5.2.0, the __tostring method will only take effect if you use Echo () or print () together. After PHP 5.2.0, you can take effect in any string environment (for example, with the%s modifier through printf (), but not in a non-string environment (such as using the%d modifier). From PHP 5.2.0, a e_recoverable_error error is reported if an object with an undefined __tostring method is converted to a string.

8, __sleep, __wakeup

__sleep serialization is used when

__wakeup Crossdress is called when the line is being serialized

Serialize () checks the class for a function that has the magic name __sleep. If so, the function will run before any serialization. It clears the object and should return an array containing all the variable names that should be serialized in the object.

The purpose of using __sleep is to close any database connections that an object might have, submit data for waiting, or perform similar cleanup tasks. In addition, this function is useful if you have very large objects and do not need to be fully stored.

Conversely, unserialize () checks for the existence of a function with the magic name __wakeup. If present, this function can reconstruct any resources that an object might have. The purpose of using __wakeup is to reconstruct any database connections that may be lost in serialization and to handle other reinitialization tasks.

9, __set_state

This static method is called when Var_export () is called (Valid from PHP 5.1.0).

The only parameter to this method is an array that contains the by array (' property ' = = value, ...) The class properties of the format arrangement.

10, __invoke (PHP 5.3.0 or later)

The __invoke method is called automatically when an attempt is made to invoke an object in a way that invokes a function.

11, __callstatic (PHP 5.3.0 or later)

It works like the __call () Magic Method, __callstatic () is to handle static method calls.

PHP does strengthen the definition of the __callstatic () method; it must be public and must be declared static. Similarly, the __call () Magic method must be defined as public, and all other magic methods must be so

PHP Magic Method