Cloning objects
Since objects are passed and assigned as references you need some way to create a copy of an object. Enter
the __clone method.
the __clone method.
Example 3: Cloning objects
<?php
class foo {
var $x;
function
setX($x) {
$this->x = $x;
}
function
getX() {
return $this->x;
}
}
$o1 = new foo;
$o1->setX(4);
$o2 = $o1->__clone();
$o1->setX(5);
if(
$o1->getX() != $o2->getX()) print("Copies are independant");
?>
Cloning is ok in programming languages, don’t feel guilty 😉
In PHP4 all the methods and variables in an Object can be accessed from outside the object – this can be rephrased as
methods and variables are always public. PHP5 introduces 3 modifiers to control the access to variables and
methods: Public, Protected and Private.
methods and variables are always public. PHP5 introduces 3 modifiers to control the access to variables and
methods: Public, Protected and Private.
Public: The method/variable can be accessed from outside the class.
Private: Only methods in the same class can access private methods or variables.
Protected: Only methods in the same class or derived classes can access proteted methods or variables.
Private: Only methods in the same class can access private methods or variables.
Protected: Only methods in the same class or derived classes can access proteted methods or variables.
Example 4: Public, protected and private
<?php
class foo {
private $x;
public function
public_foo() {
print("I'm public");
}
protected function
protected_foo() {
$this->private_foo(); //Ok because we are in the same class we can call private methods
print("I'm protected");
}
private function
private_foo() {
$this->x = 3;
print("I'm private");
}
}
class
foo2 extends foo {
public function display() {
$this->protected_foo();
$this->public_foo();
// $this->private_foo(); // Invalid! the function is private in the base class
}
}
$x = new foo();
$x->public_foo();
//$x->protected_foo(); //Invalid cannot call protected methods outside the class and derived classes
//$x->private_foo(); //Invalid private methods can only be used inside the class
$x2 = new foo2();
$x2->display();
?>
Design tip: Variables should always be private, accessing variables is not a good OOP practice, it is always
better to provide methods to get/set the variables.
better to provide methods to get/set the variables.
