<?php
class Base {
protected static $c = 'base';
public static function getC() {
return self::$c;
}
}
class Derived extends Base {
protected static $c = 'derived';
}
echo Base::getC(); // output "base"
echo Derived::getC(); // output "base", but I need "derived" here!
?>
So what's the best workaround?
The best way to solve this is to upgrade to PHP 5.3, where late static bindings are available. If that's not an option, you'll unfortunately have to redesign your class.
Based on deceze's and Undolog's input:
Undolog is right, for PHP <= 5.2 .
But with 5.3 and late static bindings it will work , just use static instead of self inside the function - now it will work...//THX # deceze for the hint
for us copy past sample scanning stackoverflow users - this will work:
class Base {
protected static $c = 'base';
public static function getC() {
return static::$c; // !! please notice the STATIC instead of SELF !!
}
}
class Derived extends Base {
protected static $c = 'derived';
}
echo Base::getC(); // output "base"
echo Derived::getC(); // output "derived"
You have to re-implment base class method; try with:
class Derived extends Base {
protected static $c = 'derived';
public static function getC() {
return self::$c;
}
}
As you see, this solution is very useless, because force to re-write all subclassed methods.
The value of self::$c depends only on the class where the method was actually implemented, not the class from which it was called.
Related
I have two classes: Action and MyAction. The latter is declared as:
class MyAction extends Action {/* some methods here */}
All I need is method in the Action class (only in it, because there will be a lot of inherited classes, and I don’t want to implement this method in all of them), which will return classname from a static call. Here is what I’m talking about:
Class Action {
function n(){/* something */}
}
And when I call it:
MyAction::n(); // it should return "MyAction"
But each declaration in the parent class has access only to the parent class __CLASS__ variable, which has the value “Action”.
Is there any possible way to do this?
__CLASS__ always returns the name of the class in which it was used, so it's not much help with a static method. If the method wasn't static you could simply use get_class($this). e.g.
class Action {
public function n(){
echo get_class($this);
}
}
class MyAction extends Action {
}
$foo=new MyAction;
$foo->n(); //displays 'MyAction'
Late static bindings, available in PHP 5.3+
Now that PHP 5.3 is released, you can use late static bindings, which let you resolve the target class for a static method call at runtime rather than when it is defined.
While the feature does not introduce a new magic constant to tell you the classname you were called through, it does provide a new function, get_called_class() which can tell you the name of the class a static method was called in. Here's an example:
Class Action {
public static function n() {
return get_called_class();
}
}
class MyAction extends Action {
}
echo MyAction::n(); //displays MyAction
Since 5.5 you can use class keyword for the class name resolution, which would be a lot faster than making function calls. Also works with interfaces.
// C extends B extends A
static::class // MyNamespace\ClassC when run in A
self::class // MyNamespace\ClassA when run in A
parent::class // MyNamespace\ClassB when run in C
MyClass::class // MyNamespace\MyClass
It's not the ideal solution, but it works on PHP < 5.3.0.
The code was copied from septuro.com
if(!function_exists('get_called_class')) {
class class_tools {
static $i = 0;
static $fl = null;
static function get_called_class() {
$bt = debug_backtrace();
if (self::$fl == $bt[2]['file'].$bt[2]['line']) {
self::$i++;
} else {
self::$i = 0;
self::$fl = $bt[2]['file'].$bt[2]['line'];
}
$lines = file($bt[2]['file']);
preg_match_all('/([a-zA-Z0-9\_]+)::'.$bt[2]['function'].'/',
$lines[$bt[2]['line']-1],
$matches);
return $matches[1][self::$i];
}
}
function get_called_class() {
return class_tools::get_called_class();
}
}
Now (when 5.3 has arrived) it's pretty simple:
http://php.net/manual/en/function.get-called-class.php
class MainSingleton {
private static $instances = array();
private static function get_called_class() {
$t = debug_backtrace();
return $t[count($t)-1]["class"];
}
public static function getInstance() {
$class = self::get_called_class();
if(!isset(self::$instances[$class]) ) {
self::$instances[$class] = new $class;
}
return self::$instances[$class];
}
}
class Singleton extends MainSingleton {
public static function getInstance()
{
return parent::getInstance();
}
protected function __construct() {
echo "A". PHP_EOL;
}
protected function __clone() {}
public function test() {
echo " * test called * ";
}
}
Singleton::getInstance()->test();
Singleton::getInstance()->test();
(PHP 5 >= 5.3.0, PHP 7)
get_called_class — The "Late Static Binding" class name
<?php
class Model
{
public static function find()
{
return get_called_class();
}
}
class User extends Model
{
}
echo User::find();
this link might be helpfull
There is no way, in the available PHP versions, to do what you want. Paul Dixon's solution is the only one. I mean, the code example, as the late static bindings feature he's talking about is available as of PHP 5.3, which is in beta.
Here is my example:
trait FileConfig {
public static function getPathForUploads() {
$paths = static::getPaths();
//etc.
}
abstract public static function getPaths(); //doesn't work. Error: "Static function SharedDefaultConfig::getPaths() should not be abstract"
abstract public function getPaths(); //OK
public static function getPaths() {} //OK
}
Class:
class AppConfig {
use FileConfig;
public static function getPaths() {
return array(...);
}
}
Call:
AppConfig::getPathForUploads();
It's nessessary to make it static and abstract (to force classes using FileConfig to implement getPaths).
I wonder how is it possible to implement method changing it's static property? Is it a good practice or there are better solutions? Will it one day become illegal?
Thank you
This is fixed in php 7, so the following code works:
<?php
error_reporting(-1);
trait FileConfig {
public static function getPathForUploads() {
echo static::getPaths();
}
abstract static function getPaths();
}
class AppConfig {
use FileConfig;
protected static function getPaths() {
return "hello world";
}
}
AppConfig::getPathForUploads();
http://sandbox.onlinephpfunctions.com/code/610f3140b056f3c3e8defb84e6b57ae61fbafbc9
But it does not actually check if the method in AppConfig is static or not during compilation. You will only get a warning when you try to call the non-static method statically: http://sandbox.onlinephpfunctions.com/code/1252f81af34f71e901994af2531104d70024a685
You do not need to make the method static to force classes using it to implement the method. You can simply use interfaces alongside.
trait FileUploadConfig {
public static function getPathForUploads() {
$paths = static::getPaths();
//etc.
}
}
The trait was left as is. I just took away the functions for the interface.
interface PathConfiguration {
public static function getPaths();
}
The interface forces the class to implement the function. I left the static in there to correspond with the trait's specification.
class AppConfig implements PathConfiguration {
use FileUploadConfig;
public static function getPaths() {
return [];
}
}
To force classes using FileConfig to implement getPaths it's not nessessary to make abstract function static. Static means that it belongs to the class that declared it. Make it protected static, add code from trait and then you could change behaviour by inheritance from your AppConfig class.
I have a protected function that is defined within a certain class. I want to be able to call this protected function outside of the class within another function. Is this possible and if so how may I achieve it
class cExample{
protected function funExample(){
//functional code goes here
return $someVar
}//end of function
}//end of class
function outsideFunction(){
//Calls funExample();
}
Technically, it is possible to invoke private and protected methods using the reflection API. However, 99% of the time doing so is a really bad idea. If you can modify the class, then the correct solution is probably to just make the method public. After all, if you need to access it outside the class, that defeats the point of marking it protected.
Here's a quick reflection example, in case this is one of the very few situations where it's really necessary:
<?php
class foo {
protected function bar($param){
echo $param;
}
}
$r = new ReflectionMethod('foo', 'bar');
$r->setAccessible(true);
$r->invoke(new foo(), "Hello World");
That's the point of OOP - encapsulation:
Private
Only can be used inside the class. Not inherited by child classes.
Protected
Only can be used inside the class and child classes. Inherited by child classes.
Public
Can be used anywhere. Inherited by child classes.
If you still want to trigger that function outside, you can declare a public method that triggers your protected method:
protected function b(){
}
public function a(){
$this->b() ;
//etc
}
If the parent's method is protected, you can use an anonymous class:
class Foo {
protected function do_foo() {
return 'Foo!';
}
}
$bar = new class extends Foo {
public function do_foo() {
return parent::do_foo();
}
}
$bar->do_foo(); // "Foo!"
https://www.php.net/manual/en/language.oop5.anonymous.php
You can override this class with another where you make this public.
class cExample2 extends cExample {
public function funExample(){
return parent::funExample()
}
}
(note this won't work with private members)
But the idea of private and protected members is to NOT BE called from outside.
Another option (PHP 7.4)
<?php
class cExample {
protected function funExample(){
return 'it works!';
}
}
$example = new cExample();
$result = Closure::bind(
fn ($class) => $class->funExample(), null, get_class($example)
)($example);
echo $result; // it works!
If you want to share code between your classes you can use traits, but it depends how you want use your function/method.
Anyway
trait cTrait{
public function myFunction() {
$this->funExample();
}
}
class cExample{
use cTrait;
protected function funExample() {
//functional code goes here
return $someVar
}//end of function
}//end of class
$object = new cExample();
$object->myFunction();
This will work, but keep in mind that you don't know what your class is made of this way. If you change the trait then all of your classes which use it will be altered as well. It's also good practice to write an interface for every trait you use.
here i can give you one example like below
<?php
class dog {
public $Name;
private function getName() {
return $this->Name;
}
}
class poodle extends dog {
public function bark() {
print "'Woof', says " . $this->getName();
}
}
$poppy = new poodle;
$poppy->Name = "Poppy";
$poppy->bark();
?>
or one another way to use with latest php
In PHP you can do this using Reflections. To invoke protected or private methods use the setAccessible() method http://php.net/reflectionmethod.setaccessible (just set it to TRUE)
I am using Laravel. i was facing issue while access protected method outside of class.
$bookingPriceDetails = new class extends BookingController {
public function quotesPrice( $req , $selectedFranchise) {
return parent::quotesPrice($req , $selectedFranchise);
}
};
return $bookingPriceDetails->quotesPrice($request , selectedFranchisees());
here BookingController is Class name from which i want to get protected method. quotesPrice( $req , $selectedFranchise) is method that i want to access in different Class.
so I'm trying to work out an issue I'm having in designing PHP classes. I've created a base class, and assigned private variables. I have child classes extending this base class, which make reference and changes to these private variables through functions of the base class. Here's an example, keep in mind I'm still confused about the difference between private and protected methods/variables (let me know if I'm doing it wrong!):
base.class.php
<?php
class Base {
private $test;
public function __construct(){
require('sub.class.php');
$sub = new Sub;
echo($this->getTest());
}
public function getTest(){
return $this->test;
}
protected function setTest($value){
$this->test = $value;
}
}
?>
sub.class.php
<?php
class Sub extends Base {
public function __construct(){
parent::setTest('hello!');
}
}
?>
So I'd expect the result to be hello! printed on the screen - instead there is nothing. There could be a fundamental misunderstanding of classes on my part, or maybe I'm just doing something wrong. Any guidance is very much appreciated! Thanks.
EDIT:
Thank you to everyone who contributed an answer - I think, despite the excellent solutions, that child classes are actually not what I need - it seems delegate classes may be more useful at this point, as I don't really need to reference the Base functions from within the other classes.
Should be like this:
base.class.php:
class Base {
private $test;
public function __construct() {
echo $this->getTest();
}
public function getTest() {
return $this->test;
}
protected function setTest($value) {
$this->test = $value;
}
}
sub.class.php:
class Sub extends Base {
public function __construct() {
parent::setTest('hello!'); // Or, $this->setTest('hello!');
parent::__construct();
}
}
main code:
require 'base.class.php';
require 'sub.class.php';
$sub = new Sub; // Will print: hello!
What exactly are late static bindings in PHP?
You definitely need to read Late Static Bindings in the PHP manual. However, I'll try to give you a quick summary.
Basically, it boils down to the fact that the self keyword does not follow the same rules of inheritance. self always resolves to the class in which it is used. This means that if you make a method in a parent class and call it from a child class, self will not reference the child as you might expect.
Late static binding introduces a new use for the static keyword, which addresses this particular shortcoming. When you use static, it represents the class where you first use it, ie. it 'binds' to the runtime class.
Those are the two basic concepts behind it. The way self, parent and static operate when static is in play can be subtle, so rather than go in to more detail, I'd strongly recommend that you study the manual page examples. Once you understand the basics of each keyword, the examples are quite necessary to see what kind of results you're going to get.
From PHP: Late Static Bindings - Manual:
As of PHP 5.3.0, PHP implements a feature called late static binding which can be used to reference the called class in the context of static inheritance.
Late static binding tries to solve that limitation by introducing a keyword that references the class that was initially called at runtime. ... It was decided not to introduce a new keyword, but rather use static that was already reserved.
Let's see an example:
<?php
class Car
{
public static function run()
{
return static::getName();
}
private static function getName()
{
return 'Car';
}
}
class Toyota extends Car
{
public static function getName()
{
return 'Toyota';
}
}
echo Car::run(); // Output: Car
echo Toyota::run(); // Output: Toyota
?>
Late static bindings work by storing the class named in the last "non-forwarding call". In case of static method calls, this is the class explicitly named (usually the one on the left of the :: operator); in case of non-static method calls, it is the class of the object. A "forwarding call" is a static one that is introduced by self::, parent::, static::, or, if going up in the class hierarchy, forward_static_call(). The function get_called_class() can be used to retrieve a string with the name of the called class and static:: introduces its scope.
There is not very obvious behavior:
The following code produces 'alphabeta'.
class alpha {
function classname(){
return __CLASS__;
}
function selfname(){
return self::classname();
}
function staticname(){
return static::classname();
}
}
class beta extends alpha {
function classname(){
return __CLASS__;
}
}
$beta = new beta();
echo $beta->selfname(); // Output: alpha
echo $beta->staticname(); // Output: beta
However, if we remove the declaration of the classname function from the beta class, we get 'alphaalpha' as the result.
I'm quoting from the book: "PHP Master write cutting-edge code".
Late static binding was a feature introduced with php 5.3. It allows
us to inherit static methods from a parent class, and to reference
the child class being called.
This means you can have an abstract class with static methods, and
reference the child class's concrete implementations by using the
static::method() notation instead of the self::method().
Feel free to take a look at the official php documentation as well:
http://php.net/manual/en/language.oop5.late-static-bindings.php
The clearest way to explain Late Static Binding is with a practicle example. I'm using it in a Template method pattern. See below.
abstract class AbstractTemplate {
public const AWESOME_LIST = [''];
public function someFunction(): void {
$awesomeList = $this->getAwesomeList();
// OUTPUT: ['harry','henk','john'];
var_dump($awesomeList);
}
/**
* This function gets static constants from CHILD classes
*/
public function getAwesomeList(): array
{
return static::AWESOME_LIST;
}
}
class ConcreteTemplate extends AbstractTemplate {
public const AWESOME_LIST = ['harry','henk','john'];
public function someFunction(): void {
parent::someFunction();
}
}
$concreteTemplate = new ConcreteTemplate();
$concreteTemplate->someFunction();
Notice the static keyword in method getAwesomeList.
Let's change a bit now:
public function getAwesomeList(): array
{
return self::AWESOME_LIST;
}
The output of the var_dump at someFunction would be:
array (size=1)
0 => string '' (length=0)
The static keyword is used in a Singleton design pattern.
See link: https://refactoring.guru/design-patterns/singleton/php/example
The simplest example to show the difference.
Note, self::$c
class A
{
static $c = 7;
public static function getVal()
{
return self::$c;
}
}
class B extends A
{
static $c = 8;
}
B::getVal(); // 7
Late static binding, note static::$c
class A
{
static $c = 7;
public static function getVal()
{
return static::$c;
}
}
class B extends A
{
static $c = 8;
}
B::getVal(); // 8
Looking at it from a "why would I use this?" perspective, it's basically a way to change the context from which the static method is being interpreted/run.
With self, the context is the one where you defined the method originally. With static, it's the one you're calling it from.
For example:
abstract class Builder {
public static function build() {
return new static;
}
}
class Member extends Builder {
public function who_am_i() {
echo 'Member';
}
}
Member::build()->who_am_i();
Also, watch if you update static variables in child classes. I found this (somewhat) unexpected result where child B updates child C:
class A{
protected static $things;
}
class B extends A {
public static function things(){
static::$things[1] = 'Thing B';
return static::$things;
}
}
class C extends A{
public static function things(){
static::$things[2] = 'Thing C';
return static::$things;
}
}
print_r(C::things());
// Array (
// [2] => Thing C
// )
B::things();
print_r(C::things());
// Array (
// [2] => Thing C
// [1] => Thing B
// )
You can fix it by declaring the same variable in each child class, for example:
class C extends A{
protected static $things; // add this and B will not interfere!
public static function things(){
static::$things[2] = 'Thing C';
return static::$things;
}
}