Constructors and Destructors
Please note that if a class has a protected variable, a subclass cannot have the same variable redefined private (must be protected or weaker). It seemed to be logical for me as a subsubclass would not know if it could see it or not but even if you declare a subclass to be final the restriction remains.
Visibility
The visibility of a property or method can be defined by prefixing the declaration with the keywords: public, protected or private. Public declared items can be accessed everywhere. Protected limits access to inherited and parent classes (and to the class that defines the item). Private limits visibility only to the class that defines the item.
Members Visibility
Class members must be defined with public, private, or protected.
Example #1 Member declaration
<?php
/**
* Define MyClass
*/
class MyClass
{
public $public = 'Public';
protected $protected = 'Protected';
private $private = 'Private';
function printHello()
{
echo $this->public;
echo $this->protected;
echo $this->private;
}
}
$obj = new MyClass();
echo $obj->public; // Works
echo $obj->protected; // Fatal Error
echo $obj->private; // Fatal Error
$obj->printHello(); // Shows Public, Protected and Private
/**
* Define MyClass2
*/
class MyClass2 extends MyClass
{
// We can redeclare the public and protected method, but not private
protected $protected = 'Protected2';
function printHello()
{
echo $this->public;
echo $this->protected;
echo $this->private;
}
}
$obj2 = new MyClass2();
echo $obj2->public; // Works
echo $obj2->private; // Undefined
echo $obj2->protected; // Fatal Error
$obj2->printHello(); // Shows Public, Protected2, Undefined
?>
Note: The PHP 4 method of declaring a variable with the var keyword is still supported for compatibility reasons (as a synonym for the public keyword). In PHP 5 before 5.1.3, its usage would generate an E_STRICT warning.
Method Visibility
Class methods must be defined with public, private, or protected. Methods without any declaration are defined as public.
Example #2 Method Declaration
<?php
/**
* Define MyClass
*/
class MyClass
{
// Declare a public constructor
public function __construct() { }
// Declare a public method
public function MyPublic() { }
// Declare a protected method
protected function MyProtected() { }
// Declare a private method
private function MyPrivate() { }
// This is public
function Foo()
{
$this->MyPublic();
$this->MyProtected();
$this->MyPrivate();
}
}
$myclass = new MyClass;
$myclass->MyPublic(); // Works
$myclass->MyProtected(); // Fatal Error
$myclass->MyPrivate(); // Fatal Error
$myclass->Foo(); // Public, Protected and Private work
/**
* Define MyClass2
*/
class MyClass2 extends MyClass
{
// This is public
function Foo2()
{
$this->MyPublic();
$this->MyProtected();
$this->MyPrivate(); // Fatal Error
}
}
$myclass2 = new MyClass2;
$myclass2->MyPublic(); // Works
$myclass2->Foo2(); // Public and Protected work, not Private
class Bar
{
public function test() {
$this->testPrivate();
$this->testPublic();
}
public function testPublic() {
echo "Bar::testPublic\n";
}
private function testPrivate() {
echo "Bar::testPrivate\n";
}
}
class Foo extends Bar
{
public function testPublic() {
echo "Foo::testPublic\n";
}
private function testPrivate() {
echo "Foo::testPrivate\n";
}
}
$myFoo = new foo();
$myFoo->test(); // Bar::testPrivate
// Foo::testPublic
?>
add a note
User Contributed NotesVisibility
omnibus at omnibus dot edu dot pl
13-Dec-2007 03:34
13-Dec-2007 03:34
phpdoc at povaddict dot com dot ar
11-Oct-2007 09:52
11-Oct-2007 09:52
Re: ference at super_delete_brose dot co dot uk
"If eval() is the answer, you’re almost certainly asking the wrong question."
<?php
eval('$result = $this->'.$var.';'); //wrong
$result = $this->$var; //right way
$var = "foo";
$this->var = "this will assign to member called 'var'.";
$this->$var = "this will assign to member called 'foo'.";
?>
Joshua Watt
29-May-2007 09:09
29-May-2007 09:09
I couldn't find this documented anywhere, but you can access protected and private member varaibles in different instance of the same class, just as you would expect
i.e.
<?php
class A
{
protected $prot;
private $priv;
public function __construct($a, $b)
{
$this->prot = $a;
$this->priv = $b;
}
public function print_other(A $other)
{
echo $other->prot;
echo $other->priv;
}
}
class B extends A
{
}
$a = new A("a_protected", "a_private");
$other_a = new A("other_a_protected", "other_a_private");
$b = new B("b_protected", "ba_private");
$other_a->print_other($a); //echoes a_protected and a_private
$other_a->print_other($b); //echoes b_protected and ba_private
$b->print_other($a); //echoes a_protected and a_private
?>
ference at super_delete_brose dot co dot uk
22-May-2007 07:10
22-May-2007 07:10
Sometimes you may wish to have all members of a class visible to other classes, but not editable - effectively read-only.
In this case defining them as public or protected is no good, but defining them as private is too strict and by convention requires you to write accessor functions.
Here is the lazy way, using one get function for accessing any of the variables:
<?php
class Foo {
private $a;
private $b;
private $c;
private $d;
private $e;
private $f;
public function __construct() {
$this->a = 'Value of $a';
$this->b = 'Value of $b';
$this->c = 'Value of $c';
$this->d = 'Value of $d';
$this->e = 'Value of $e';
$this->f = 'Value of $f';
}
/* Accessor for all class variables. */
public function get($what) {
$result = FALSE;
$vars = array_keys(get_class_vars('Foo'));
foreach ($vars as $var) {
if ($what == $var) {
eval('$result = $this->'.$var.';');
return $result;
}
}
return $result;
}
}
class Bar {
private $a;
public function __construct() {
$foo = new Foo();
var_dump($foo->get('a')); // results in: string(11) "Value of $a"
}
}
$bar = new Bar();
?>
nanocaiordo at gmail dot com
08-Apr-2007 03:49
08-Apr-2007 03:49
If you always thought how can you use a private method in php4 classes then try the following within your class.
<?php
function private_func($func)
{
$this->file = __FILE__;
if (PHPVERS >= 43) {
$tmp = debug_backtrace();
for ($i=0; $i<count($tmp); ++$i) {
if (isset($tmp[$i]['function'][$func])) {
if ($this->file != $tmp[$i]['file']) {
trigger_error('Call to a private method '.__CLASS__.'::'.$func.' in '.$tmp[$i]['file'], E_USER_ERROR);
}
}
}
}
}
?>
Then inside the private function add:
<?php
function foo() {
$this->private_func(__FUNCTION__);
# your staff goes here
}
?>
Alex
14-Mar-2007 06:33
14-Mar-2007 06:33
Uh... to atitthaker at gmail dot com -- It is *meant* to be available under C as well, since A is a superclass of C, and any proctected methods in a superclass is always available to a subclass, no matter how many "generations" you have to traverse, it is available to C.
atitthaker at gmail dot com
01-Mar-2007 10:34
01-Mar-2007 10:34
<?
class A
{
protected $b=20;
private $a=10;
//protected method and shall not be accessible under class C
protected function access()
{
print("here");
}
}
class B extends A
{
public function test()
{
$this->access() ;
}
}
class C extends B
{
function temp()
{
$this->access(); // access variable and prints "here"
}
}
$abc= new C();
$abc->temp();
?>
Above code shall generate error as protected method of class A is accessible in class C which is directly not inheriting class A.
stephane at harobed dot org
23-Aug-2006 11:22
23-Aug-2006 11:22
A class A static public function can access to class A private function :
<?php
class A {
private function foo()
{
print("bar");
}
static public function bar($a)
{
$a->foo();
}
}
$a = new A();
A::bar($a);
?>
It's working.
kakugo at kakugo dot com
13-Jul-2006 12:19
13-Jul-2006 12:19
This refers to previous notes on protected members being manipulated externally:
It is obvious that if you were to allow methods the option of replacing protected variables with external ones it will be possible, but there is no reason not to simply use a protected method to define these, or not to write the code to allow it. Just because it is possible doesn't mean it's a problem, it simply does not allow you to be lax on the security of the class.
LoN_Kamikaze at gmx dot de
28-Mar-2006 11:26
28-Mar-2006 11:26
About the previous note:
Of course you cannot declare public attributes/methods private, because it can break code relying on access to such an attribute/method. But of course your children can override private with protected/public.
c3 at epetersen dot org
07-Feb-2006 02:50
07-Feb-2006 02:50
Note that you cannot change visibility in a child defined in the parent:
class A {
public function f() {}
}
class B extends A {
private function f() {}
}
Produces Fatal error: Access level to B::f() must be public (as in class A) in ...
jfk, visibility != security. Visibility prevents programmers from doing dumb things like:
class A {
private function __construct() {}
final public static &factory() { return new A(); }
}
$x = new A();
The use of "protected" as an identifier is unfortunate tradition as it really means "only me and my decedents" (and in the odd case of PHP my ancestors too).
r dot wilczek at web-appz dot de
05-Jan-2006 02:11
05-Jan-2006 02:11
Beware: Visibility works on a per-class-base and does not prevent instances of the same class accessing each others properties!
<?php
class Foo
{
private $bar;
public function debugBar(Foo $object)
{
// this does NOT violate visibility although $bar is private
echo $object->bar, "\n";
}
public function setBar($value)
{
// Neccessary method, for $bar is invisible outside the class
$this->bar = $value;
}
public function setForeignBar(Foo $object, $value)
{
// this does NOT violate visibility!
$object->bar = $value;
}
}
$a = new Foo();
$b = new Foo();
$a->setBar(1);
$b->setBar(2);
$a->debugBar($b); // 2
$b->debugBar($a); // 1
$a->setForeignBar($b, 3);
$b->setForeignBar($a, 4);
$a->debugBar($b); // 3
$b->debugBar($a); // 4
?>
gugglegum at gmail dot com
02-Sep-2005 12:14
02-Sep-2005 12:14
Private visibility actually force members to be not inherited instead of limit its visibility. There is a small nuance that allows you to redeclare private member in child classes.
<?php
class A
{
private $prop = 'I am property of A!';
}
class B extends A
{
public $prop = 'I am property of B!';
}
$b = new B();
echo $b->prop; // "I am property of B!"
?>
Miguel <miguel at lugopolis dot net>
21-Jul-2005 05:10
21-Jul-2005 05:10
A note about private members, the doc says "Private limits visibility only to the class that defines the item" this says that the following code works as espected:
<?php
class A {
private $_myPrivate="private";
public function showPrivate()
{
echo $this->_myPrivate."\n";
}
}
class B extends A {
public function show()
{
$this->showPrivate();
}
}
$obj=new B();
$obj->show(); // shows "private\n";
?>
this works cause A::showPrivate() is defined in the same class as $_myPrivate and has access to it.