Example
Members of objects or classes can be accessed using the object operator (->) and the class operator (::).
class MyClass {
public $a = 1;
public static $b = 2;
const C = 3;
public function d() { return 4; }
public static function e() { return 5; }
}
$object = new MyClass();
var_dump($object->a); // int(1)
var_dump($object::$b); // int(2)
var_dump($object::C); // int(3)
var_dump(MyClass::$b); // int(2)
var_dump(MyClass::C); // int(3)
var_dump($object->d()); // int(4)
var_dump($object::d()); // int(4)
var_dump(MyClass::e()); // int(5)
$classname = "MyClass";
var_dump($classname::e()); // also works! int(5)
Note that after the object operator, the $ should not be written ($object->a instead of $object->$a). For the class operator, this is not the case and the $ is necessary. For a constant defined in the class, the $ is never used.
Also note that var_dump(MyClass::d()); is only allowed if the function d() does not reference the object:
class MyClass {
private $a = 1;
public function d() {
return $this->a;
}
}
$object = new MyClass();
var_dump(MyClass::d()); // Error!
This causes a 'PHP Fatal error: Uncaught Error: Using $this when not in object context'
These operators have left associativity, which can be used for 'chaining':
class MyClass {
private $a = 1;
public function add(int $a) {
$this->a += $a;
return $this;
}
public function get() {
return $this->a;
}
}
$object = new MyClass();
var_dump($object->add(4)->get()); // int(5)
These operators have the highest precedence (they are not even mentioned in the manual), even higher that clone. Thus:
class MyClass {
private $a = 0;
public function add(int $a) {
$this->a += $a;
return $this;
}
public function get() {
return $this->a;
}
}
$o1 = new MyClass();
$o2 = clone $o1->add(2);
var_dump($o1->get()); // int(2)
var_dump($o2->get()); // int(2)
The value of $o1 is added to before the object is cloned!
Note that using parentheses to influence precedence did not work in PHP version 5 and older (it does in PHP 7):
// using the class MyClass from the previous code
$o1 = new MyClass();
$o2 = (clone $o1)->add(2); // Error in PHP 5 and before, fine in PHP 7
var_dump($o1->get()); // int(0) in PHP 7
var_dump($o2->get()); // int(2) in PHP 7
