Examples of magic methods in php

PHP provides a series of magic methods for object-oriented programming, in PHP, the methods starting with two underscores _ are called Magic methods. these magic methods do not need to be called, but start with a specific condition. This chapter gives you a brief introduction to the magic methods provided in PHP. What is magic?

PHP provides a series of magic methods for object-oriented programming, in PHP, the methods starting with two underscores _ are called Magic methods. these magic methods do not need to be called, but start with a specific condition. This chapter gives you a brief introduction to the magic methods provided in PHP.

The following table lists the PHP magic methods:

Function	Description
_ Construct ()	Class constructor
_ Destruct ()	Class destructor
_ Call ()	Called when an inaccessible method is called in an object
_ CallStatic ()	Call an inaccessible method in static mode
_ Get ()	Called when obtaining a class member variable
_ Set ()	Called when setting a class member variable
_ Isset ()	When isset () or empty () is called for an inaccessible attribute
_ Unset ()	This API is called when unset () is called for an inaccessible attribute.
_ Sleep ()	This function is called first when serialize () is executed.
_ Wakeup ()	This function is called first when unserialize () is executed.
_ ToString ()	Response method when the class is treated as a string
_ Invoke ()	Method of calling a function to call an object
_ Set_state ()	This static method is called when var_export () is called to export the class.
_ Clone ()	Called when the object copy is complete

In the table above, "_" is two underscores instead of one "_".

Next, let's take a look at the examples and applications of these magic methods.

_ Construct () and _ destruct ()

Constructor and destructor should not be unfamiliar. they are called when the object is created or eliminated. For example, we need to open a file, which is opened when the object is created, and closed when the object is killed.

 handle = fopen(...);    }    function __destruct(){        fclose($this->handle);    }}?>

These two methods can be extended during inheritance, for example:

_ Call () and _ callStatic ()

When an inaccessible method is called in an object, the two methods are called, and the latter is a static method. These two methods may be used in Variable functions calls.

 runTest('in object context');MethodTest::runTest('in static context');?>

_ Get () ,__ set () ,__ isset () and _ unset ()

These two functions are called when get/set is a member variable of a class. For example, we save the object variables in another array, instead of the member variables of the object.

 data[$name] = $value;    }    public function __get($name){        if(array_key_exists($name, $this->data))            return $this->data[$name];        return NULL;    }    public function __isset($name){        return isset($this->data[$name]);    }    public function __unset($name){        unset($this->data[$name]);    }}?>

_ Sleep () and _ wakeup ()

When we execute serialize () and unserialize (), these two functions are called first. For example, when we serialize an object, this object has a database link. to restore the link status in deserialization, we can reconstruct these two functions to restore the link.

Example:

 server = $server;        $this->username = $username;        $this->password = $password;        $this->db = $db;        $this->connect();    }    private function connect()    {        $this->link = mysql_connect($this->server, $this->username, $this->password);        mysql_select_db($this->db, $this->link);    }    public function __sleep()    {        return array('server', 'username', 'password', 'db');    }    public function __wakeup()    {        $this->connect();    }}?>

_ ToString ()

Response method when the object is treated as a string. For example, echo $ obj; is used to output an object.

This method can only return a string and cannot throw an exception in this method. Otherwise, a fatal error occurs.

_ Invoke ()

The response method when a function is called. As follows:

_ Set_state ()

This static method is called when var_export () is called to export the class.

 var1 = $an_array['var1'];        $obj->var2 = $an_array['var2'];        return $obj;    }}$a = new A;$a->var1 = 5;$a->var2 = 'foo';var_dump(var_export($a));?>

_ Clone ()

Called when the object copy is complete. For example, detailed description of the design mode and PHP implementation: This function is used to prevent the object from being cloned.

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