Detailed explanation of php magic method comparison and use of example code

In PHP, methods starting with two underscores are called magic methods. These methods play a decisive role in PHP.

construct() and destruct()

Constructor functionand destructor should be familiar, they are used in object creation and destruction is called when. For example, we need to open a file, open it when the object is created, and close it when the object dies

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

These two methods can be expanded when inheriting, for example:

call() and callStatic()

These two methods will be called when an inaccessible method is called in the object, and the latter is a static method. These two methods may be used in variable method (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 a member variable of a class. For example, we save the object variables in another array instead of the member variables of the object itself

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 are executing serialize () and unserialize(), these two functions will be called first. For example, when we serialize an object, the object has a database link. If we want to restore the link state during deserialization, we can restore the link by reconstructing these two functions. Examples are as follows:

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()

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

This method can only return a string, and you cannotthrow an exceptionin this method, otherwise a fatal error will occur.

invoke()

The response method when calling an object by calling a function. As follows

set_state()

When calling var_export() to export a class, this static method will be called.

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 completed. For example, in the singleton mode implementation method mentioned in the article Detailed Explanation of Design Patterns and PHP Implementation: Singleton Mode, this function is used to prevent objects from being cloned.

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