PHP Magic Methods

These are the following magic methods available

__construct, __destruct, __call, __callStatic, __get, __set, __isset, __unset, __sleep, __wakeup, __toString, __invoke, __set_state and __clone are magical in PHP classes.

PHP reserves all function names starting with __ as magical.

__sleep
serialize() checks if your class has a function with the magic name __sleep. If so, that function is executed prior to any serialization. It can clean up the object and is supposed to return an array with the names of all variables of that object that should be serialized. If the method doesn’t return anything then NULL is serialized and E_NOTICE is issued.

__wakeup
Conversely, unserialize() checks for the presence of a function with the magic name __wakeup. If present, this function can reconstruct any resources that the object may have.

Example:
class Connection {
protected $link;
private $server, $username, $password, $db;

public function __construct($server, $username, $password, $db)
{
$this->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 __toString method allows a class to decide how it will react when it is converted to a string.

Example
class Member
{
private $m_szEmail;
private $m_szUsername;

public function __construct($szUsername, $szEmail)
{
$this->m_szUsername = $szUsername;
$this->m_szEmail = $szEmail;
}
}

$pMember = new Member('Karl', 'karl@talkphp.com');

echo $pMember;

O/P is object.

Usually, most people would achieve this with code like:

echo $pMember->getUsername() . " (" . $pMember->getEmail() . ")";

However, what we can do is use the __toString() function to change the default behaviour of the object to string conversion. This would allow us to specify exactly
Add this method in your class

public function __toString()
{
return sprintf('%s (%s)', $this->m_szUsername, $this->m_szEmail);
}

__set() is run when writing data to inaccessible properties.

__get() is utilized for reading data from inaccessible properties.

__isset() is triggered by calling isset() or empty() on inaccessible properties.

__unset() is invoked when unset() is used on inaccessible properties.

__call() is triggered when invoking inaccessible methods in an object context.

__callStatic() is triggered when invoking inaccessible methods in a static context.

__invoke() this method is called when a script tries to call an object as a function.

__set_state() This static method is called for classes exported by var_export() since PHP 5.1.0.

The only parameter of this method is an array containing exported properties in the form array('property' => value, ...).