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.
Note:
It is not possible for __sleep() to return names of private properties in parent classes. Doing this will result in an
E_NOTICElevel error. Instead you may use the Serializable interface.
The intended use of __sleep() is to commit pending data or perform similar cleanup tasks. Also, the function is useful if you have very large objects which do not need to be saved completely.
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.
The intended use of __wakeup() is to reestablish any database connections that may have been lost during serialization and perform other reinitialization tasks.
<?php
class Connection
{
protected $link;
private $dsn, $username, $password;
public function __construct($dsn, $username, $password)
{
$this->dsn = $dsn;
$this->username = $username;
$this->password = $password;
$this->connect();
}
private function connect()
{
$this->link = new PDO($this->dsn, $this->username, $this->password);
}
public function __sleep()
{
return array('dsn', 'username', 'password');
}
public function __wakeup()
{
$this->connect();
}
}?>
<?php
// Declare a simple class
class TestClass
{
public $foo;
public function __construct($foo)
{
$this->foo = $foo;
}
public function __toString()
{
return $this->foo;
}
}
$class = new TestClass('Hello');
echo $class;
?>
The above example will output:
Hello
The __invoke() method is called when a script tries to call an object as a function.
Note:
This feature is available since PHP 5.3.0.
<?php
class CallableClass
{
public function __invoke($x)
{
var_dump($x);
}
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>
The above example will output:
int(5) bool(true)
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, ...).
<?php
class A
{
public $var1;
public $var2;
public static function __set_state($an_array) // As of PHP 5.1.0
{
$obj = new A;
$obj->var1 = $an_array['var1'];
$obj->var2 = $an_array['var2'];
return $obj;
}
}
$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';
eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
// 'var1' => 5,
// 'var2' => 'foo',
// ));
var_dump($b);
?>
The above example will output:
object(A)#2 (2) {
["var1"]=>
int(5)
["var2"]=>
string(3) "foo"
}
This method is called by var_dump() when dumping an object to get the properties that should be shown. If the method isn't defined on an object, then all public, protected and private properties will be shown.
This feature was added in PHP 5.6.0.
<?php
class C {
private $prop;
public function __construct($val) {
$this->prop = $val;
}
public function __debugInfo() {
return [
'propSquared' => $this->prop ** 2,
];
}
}
var_dump(new C(42));
?>
The above example will output:
object(C)#1 (1) {
["propSquared"]=>
int(1764)
}
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