Related
I am using PHP.
As properties defined within the core of a class must be static, I have to create one property in the constructor to allow me to create it with a dynamic name.
Example
final class User extends Z
{
}
Abstract Class Z
{
function __constructor()
{
$x = get_called_class() . 'Id';
$this->$x = null;
}
}
If we var_dump() obj User we would have
object(User)#1 (1) {
["UserId"]=>
NULL
}
I want to set property A as a protected type.
How can I do this?
Or is there a better way to set the name of my dynamically named property?
The best you can probably do is use magic getter/setter methods and an array of properties:
<?php
abstract class Z
{
private $properties = array();
function __construct()
{
$x = get_called_class();
$this->$x = null;
}
public function __set($prop, $val)
{
$this->properties[$prop] = $val;
}
public function __get($prop)
{
return $this->properties[$prop];
}
}
class A extends Z
{
}
var_dump(new A());
Note that the property is private, child classes will have to go through the __get and __set methods.
You could also restrict dynamic properties to only be the called class name.
<?php
abstract class Z
{
private $classprop;
function __construct()
{
$x = get_called_class();
$this->$x = true;
}
public function __set($prop, $val)
{
if ($prop !== get_called_class()) {
throw new \UnexpectedValueException('Cannot Set Dynamic properties Other than Class Name');
}
$this->classprop = $val;
}
public function __get($prop)
{
if ($prop !== get_called_class()) {
throw new \UnexpectedValueException('Cannot Get Dynamic properties Other than Class Name');
}
return $this->classprop;
}
}
class A extends Z
{
}
I would encourage you to think pretty carefully about why you need dynamic properties like this.
The easiest answer would be don't - just use some generic base property, like protected $Id; and save the trouble.
If you really must have "dynamic" properties in class extensions, probably the simplest would be to declare the property in the extending class:
final class User extends Z {
protected $UserId;
}
Then your code in Z will pick out this protected property. It's psudo-dynamic, since the property name is determined by the coder, and the script only "finds" it when the constructor is run, but if your property name is already determined by something fixed at compile-time, such as the class name, there's functionally no difference.
For truly dynamic property creation, you'd have to add in a runkit, an extension that allows you to programmatically change classes, methods, properties, and functions from within the script itself. A good one seems to be this one by Demitry Zenovich. Unless you have some truly complex functions to carry out to justify the time working with it, though, it ain't going to make your life easier.
I'm wondering why the following code won't print out anything. I'm trying to access Bar::$some_var from method in parent class. Where Bar::$some_var is defined in it's constructor.
I've tried using self::$some_var and static::$some_var in Foo::hello() but neither worked. Do I have to make $some_var static?
class Foo {
private $some_var;
public function __construct() {
$this->some_var = 5;
}
public function hello() {
print $this->some_var;
}
}
class Bar extends Foo {
public function __construct() {
$this->some_var = 10;
}
}
$bar = new Bar();
$bar->hello();
Thanks in advance.
private makes a member variable unavailable outside of a class. You need to use protected to allow extending classes to have access to that variable.
protected $some_var;
See Visibility
Your class variable cannot be private if you would like your child class to access it.
Try protected instead and it should work!
:: operator is used to access class items (constants, static
variables, static methods)
-> operator is used to access object items (non static properties and methods)
anyway in your code the problem is visibility of $some_var. It has to be almost protected, public will also work
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.
I'm building a User Class for my new website, however this time I was thinking to build it little bit differently...
C++, Java and even Ruby (and probably other programming languages) are allowing the use of nested/inner classes inside the main class, which allows us to make the code more object-oriented and organized.
In PHP, I would like to do something like so:
<?php
public class User {
public $userid;
public $username;
private $password;
public class UserProfile {
// some code here
}
private class UserHistory {
// some code here
}
}
?>
Is that possible in PHP? How can I achieve it?
UPDATE
If it's impossible, will future PHP versions might support nested classes?
Intro:
Nested classes relate to other classes a little differently than outer classes. Taking Java as an example:
Non-static nested classes have access to other members of the enclosing class, even if they are declared private. Also, non-static nested classes require an instance of the parent class to be instantiated.
OuterClass outerObj = new OuterClass(arguments);
outerObj.InnerClass innerObj = outerObj.new InnerClass(arguments);
There are several compelling reasons for using them:
It is a way of logically grouping classes that are only used in one place.
If a class is useful to only one other class, then it is logical to
relate and embed it in that class and keep the two together.
It increases encapsulation.
Consider two top-level classes, A and B, where B needs access to
members of A that would otherwise be declared private. By hiding class
B within class A, A's members can be declared private and B can access
them. In addition, B itself can be hidden from the outside world.
Nested classes can lead to more readable and maintainable code.
A nested class usually relates to it's parent class and together form a "package"
In PHP
You can have similar behavior in PHP without nested classes.
If all you want to achieve is structure/organization, as Package.OuterClass.InnerClass, PHP namespaces might sufice. You can even declare more than one namespace in the same file (although, due to standard autoloading features, that might not be advisable).
namespace;
class OuterClass {}
namespace OuterClass;
class InnerClass {}
If you desire to emulate other characteristics, such as member visibility, it takes a little more effort.
Defining the "package" class
namespace {
class Package {
/* protect constructor so that objects can't be instantiated from outside
* Since all classes inherit from Package class, they can instantiate eachother
* simulating protected InnerClasses
*/
protected function __construct() {}
/* This magic method is called everytime an inaccessible method is called
* (either by visibility contrains or it doesn't exist)
* Here we are simulating shared protected methods across "package" classes
* This method is inherited by all child classes of Package
*/
public function __call($method, $args) {
//class name
$class = get_class($this);
/* we check if a method exists, if not we throw an exception
* similar to the default error
*/
if (method_exists($this, $method)) {
/* The method exists so now we want to know if the
* caller is a child of our Package class. If not we throw an exception
* Note: This is a kind of a dirty way of finding out who's
* calling the method by using debug_backtrace and reflection
*/
$trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 3);
if (isset($trace[2])) {
$ref = new ReflectionClass($trace[2]['class']);
if ($ref->isSubclassOf(__CLASS__)) {
return $this->$method($args);
}
}
throw new \Exception("Call to private method $class::$method()");
} else {
throw new \Exception("Call to undefined method $class::$method()");
}
}
}
}
Use case
namespace Package {
class MyParent extends \Package {
public $publicChild;
protected $protectedChild;
public function __construct() {
//instantiate public child inside parent
$this->publicChild = new \Package\MyParent\PublicChild();
//instantiate protected child inside parent
$this->protectedChild = new \Package\MyParent\ProtectedChild();
}
public function test() {
echo "Call from parent -> ";
$this->publicChild->protectedMethod();
$this->protectedChild->protectedMethod();
echo "<br>Siblings<br>";
$this->publicChild->callSibling($this->protectedChild);
}
}
}
namespace Package\MyParent
{
class PublicChild extends \Package {
//Makes the constructor public, hence callable from outside
public function __construct() {}
protected function protectedMethod() {
echo "I'm ".get_class($this)." protected method<br>";
}
protected function callSibling($sibling) {
echo "Call from " . get_class($this) . " -> ";
$sibling->protectedMethod();
}
}
class ProtectedChild extends \Package {
protected function protectedMethod() {
echo "I'm ".get_class($this)." protected method<br>";
}
protected function callSibling($sibling) {
echo "Call from " . get_class($this) . " -> ";
$sibling->protectedMethod();
}
}
}
Testing
$parent = new Package\MyParent();
$parent->test();
$pubChild = new Package\MyParent\PublicChild();//create new public child (possible)
$protChild = new Package\MyParent\ProtectedChild(); //create new protected child (ERROR)
Output:
Call from parent -> I'm Package protected method
I'm Package protected method
Siblings
Call from Package -> I'm Package protected method
Fatal error: Call to protected Package::__construct() from invalid context
NOTE:
I really don't think trying to emulate innerClasses in PHP is such a good idea. I think the code is less clean and readable. Also, there are probably other ways to achieve similar results using a well established pattern such as the Observer, Decorator ou COmposition Pattern. Sometimes, even simple inheritance is sufficient.
Real nested classes with public/protected/private accessibility were proposed in 2013 for PHP 5.6 as an RFC but did not make it (No voting yet, no update since 2013 - as of 2021/02/03):
https://wiki.php.net/rfc/nested_classes
class foo {
public class bar {
}
}
At least, anonymous classes made it into PHP 7
https://wiki.php.net/rfc/anonymous_classes
From this RFC page:
Future Scope
The changes made by this patch mean named nested classes are easier to implement (by a tiny bit).
So, we might get nested classes in some future version, but it's not decided yet.
You cannot do this in PHP. However, there are functional ways to accomplish this.
For more details please check this post:
How to do a PHP nested class or nested methods?
This way of implementation is called fluent interface: http://en.wikipedia.org/wiki/Fluent_interface
As per Xenon's comment to Anıl Özselgin's answer, anonymous classes have been implemented in PHP 7.0, which is as close to nested classes as you'll get right now. Here are the relevant RFCs:
Nested Classes (status: withdrawn)
Anonymous Classes (status: implemented in PHP 7.0)
An example to the original post, this is what your code would look like:
<?php
public class User {
public $userid;
public $username;
private $password;
public $profile;
public $history;
public function __construct() {
$this->profile = new class {
// Some code here for user profile
}
$this->history = new class {
// Some code here for user history
}
}
}
?>
This, though, comes with a very nasty caveat. If you use an IDE such as PHPStorm or NetBeans, and then add a method like this to the User class:
public function foo() {
$this->profile->...
}
...bye bye auto-completion. This is the case even if you code to interfaces (the I in SOLID), using a pattern like this:
<?php
public class User {
public $profile;
public function __construct() {
$this->profile = new class implements UserProfileInterface {
// Some code here for user profile
}
}
}
?>
Unless your only calls to $this->profile are from the __construct() method (or whatever method $this->profile is defined in) then you won't get any sort of type hinting. Your property is essentially "hidden" to your IDE, making life very hard if you rely on your IDE for auto-completion, code smell sniffing, and refactoring.
Since PHP version 5.4 you can force create objects with private constructor through reflection. It can be used to simulate Java nested classes. Example code:
class OuterClass {
private $name;
public function __construct($name) {
$this->name = $name;
}
public function getName() {
return $this->name;
}
public function forkInnerObject($name) {
$class = new ReflectionClass('InnerClass');
$constructor = $class->getConstructor();
$constructor->setAccessible(true);
$innerObject = $class->newInstanceWithoutConstructor(); // This method appeared in PHP 5.4
$constructor->invoke($innerObject, $this, $name);
return $innerObject;
}
}
class InnerClass {
private $parentObject;
private $name;
private function __construct(OuterClass $parentObject, $name) {
$this->parentObject = $parentObject;
$this->name = $name;
}
public function getName() {
return $this->name;
}
public function getParent() {
return $this->parentObject;
}
}
$outerObject = new OuterClass('This is an outer object');
//$innerObject = new InnerClass($outerObject, 'You cannot do it');
$innerObject = $outerObject->forkInnerObject('This is an inner object');
echo $innerObject->getName() . "\n";
echo $innerObject->getParent()->getName() . "\n";
You can't do it in PHP. PHP supports "include", but you can't even do that inside of a class definition. Not a lot of great options here.
This doesn't answer your question directly, but you may be interested in "Namespaces", a terribly ugly\syntax\hacked\on\top\of PHP OOP:
http://www.php.net/manual/en/language.namespaces.rationale.php
I think I wrote an elegant solution to this problem by using namespaces. In my case, the inner class does not need to know his parent class (like the static inner class in Java). As an example I made a class called 'User' and a subclass called 'Type', used as a reference for the user types (ADMIN, OTHERS) in my example. Regards.
User.php (User class file)
<?php
namespace
{
class User
{
private $type;
public function getType(){ return $this->type;}
public function setType($type){ $this->type = $type;}
}
}
namespace User
{
class Type
{
const ADMIN = 0;
const OTHERS = 1;
}
}
?>
Using.php (An example of how to call the 'subclass')
<?php
require_once("User.php");
//calling a subclass reference:
echo "Value of user type Admin: ".User\Type::ADMIN;
?>
You can, like this, in PHP 7:
class User{
public $id;
public $name;
public $password;
public $Profile;
public $History; /* (optional declaration, if it isn't public) */
public function __construct($id,$name,$password){
$this->id=$id;
$this->name=$name;
$this->name=$name;
$this->Profile=(object)[
'get'=>function(){
return 'Name: '.$this->name.''.(($this->History->get)());
}
];
$this->History=(object)[
'get'=>function(){
return ' History: '.(($this->History->track)());
}
,'track'=>function(){
return (lcg_value()>0.5?'good':'bad');
}
];
}
}
echo ((new User(0,'Lior','nyh'))->Profile->get)();
It is waiting for voting as RFC
https://wiki.php.net/rfc/anonymous_classes
This page keeps coming up in my Internet searches on this subject so figured I should chime in even though this is an 8-year old post. The documentation for PHP5 demonstrates that anonymous classes can be defined within a class method. The object created can extend, implement, and even use other classes, interfaces, and traits. Consider the following OOP paradigm of factory object production. Similar to what #e-i-pi pointed out ...
class Factory {
/**
* Method to manufacture an inner-class object.
*
* #param string $args Arguments to be passed to
* the inner-class constructor.
*/
static function manufacture_object($args) {
/**
* Here's the definition of the inner-class.
*/
return new class($args) {
static $remembers = 'Nothing';
private $args;
function __construct($args) {
$this->$args = $args;
}
function says() {
return $this->args;
}
};
}
}
/**
* Create an inner-class object and have it do its thing.
*/
$mort = Factory::manufacture_object("Hello World!");
echo $mort->says(); // Echoes "Hello World!"
The objects are one-off, so one would expect the static values of the objects returned would not bind from one instance to another. After all, the anonymous class is unique from one object to another. However, late static binding works as one would otherwise expect from a nested class.
$mort = Factory::manufacture_object("I can remember that.");
$mort2 = Factory::manufacture_object("I'll live vicariously through you.");
$mort::$remembers = 'Something';
echo $mort2::$remembers; // Echoes "Something"
So, there you go: inner/nested classes and creation of their objects with static functionality has been possible since September 22, 2013 (right about the time this question was asked).
Put each class into separate files and "require" them.
User.php
<?php
class User {
public $userid;
public $username;
private $password;
public $profile;
public $history;
public function __construct() {
require_once('UserProfile.php');
require_once('UserHistory.php');
$this->profile = new UserProfile();
$this->history = new UserHistory();
}
}
?>
UserProfile.php
<?php
class UserProfile
{
// Some code here
}
?>
UserHistory.php
<?php
class UserHistory
{
// Some code here
}
?>
I understand that there are two ways to access a PHP class - "::" and "->". Sometime one seems to work for me, while the other doesn't, and I don't understand why.
What are the benefits of each, and what is the right situation to use either?
Simply put, :: is for class-level properties, and -> is for object-level properties.
If the property belongs to the class, use ::
If the property belongs to an instance of the class, use ->
class Tester
{
public $foo;
const BLAH;
public static function bar(){}
}
$t = new Tester;
$t->foo;
Tester::bar();
Tester::BLAH;
The "::" symbol is for accessing methods / properties of an object that have been declared with the static keyword, "->" is for accessing the methods / properties of an object that represent instance methods / properties.
Php can be confusing in this regard you should read this.
What's also confusing is that you can call non static functions with the :: symbol. This is very strange when you come from Java. And it certainly surprised me when I first saw it.
For example:
class Car
{
public $name = "Herbie <br/>";
public function drive()
{
echo "driving <br/>";
}
public static function gas()
{
echo "pedal to the metal<br/>";
}
}
Car::drive(); //will work
Car::gas(); //will work
$car = new Car();
$car->drive(); // will work
$car->gas(); //will work
echo $car->name; // will work
echo Car::$name; // wont work error
As you can see static is very loose in php. And you can call any function with both the -> and the :: symbols. But there is a difference when you call with :: there is no $this reference to an instance. See example #1 in the manual.
When you declare a class, it is by default 'static'. You can access any method in that class using the :: operator, and in any scope. This means if I create a lib class, I can access it wherever I want and it doesn't need to be globaled:
class lib
{
static function foo()
{
echo "hi";
}
}
lib::foo(); // prints hi
Now, when you create an instance of this class by using the new keyword, you use -> to access methods and values, because you are referring to that specific instance of the class. You can think of -> as inside of. (Note, you must remove the static keyword) IE:
class lib
{
function foo()
{
echo "hi";
}
}
$class = new lib;
$class->foo(); // I am accessing the foo() method INSIDE of the $class instance of lib.
It should also be noted that every static function can also be called using an instance of the class but not the other way around.
So this works:
class Foo
{
public static function bar(){}
}
$f = new Foo();
$f->bar(); //works
Foo::bar(); //works
And this doesn't:
class Foo
{
protected $test="fddf";
public function bar(){ echo $this->test; }
}
$f = new Foo();
$f->bar(); //works
Foo::bar(); //fails because $this->test can't be accessed from a static call
Of course you should restrict yourself to calling static methods in a static way, because instantiating an instance not only costs memory but also doesn't make much sense.
This explanation was mainly to illustrate why it worked for you some of the times.
:: is used to access a class static property. And -> is used to access a class instance ( Object's ) property.
Consider this Product class that has two functions for retrieving product details. One function getProductDetails belongs to the instance of a class, while the other getProductDetailsStatic belongs to the class only.
class Product {
protected $product_id;
public function __construct($product_id) {
$this->product_id = $product_id;
}
public function getProductDetails() {
$sql = "select * from products where product_id= $this->product_id ";
return Database::execute($sql);
}
public static function getProductDetailsStatic($product_id) {
$sql = "select * from products where product_id= $product_id ";
return Database::execute($sql);
}
}
Let's Get Products:
$product = new Product('129033'); // passing product id to constructor
var_dump( $product->getProductDetails() ); // would get me product details
var_dump( Product::getProductDetailsStatic('129033') ); // would also get me product details
When to you use Static properties?
Consider this class that may not require a instantiation:
class Helper {
static function bin2hex($string = '') {
}
static function encryptData($data = '') {
}
static function string2Url($string = '') {
}
static function generateRandomString() {
}
}
Sourcing WikiPedia - Class
In object-oriented programming, a
class is a programming language
construct that is used as a blueprint
to create objects. This blueprint
describes the state and behavior that
the created objects all share. An
object created by a class is an
instance of the class, and the class
that created that instance can be
considered as the type of that object,
e.g. a type of an object created by a
"Fruit" class would be "Fruit".
The :: operator accesses class methods and properties which are defined in php using the static keyword. Class const are also accessed using ::
The -> operator accesses methods and properties of an Instance of the class.
If the function operates on an instance, you'll be using ->. If it operates on the class itself, you'll be using ::
Another use of :: would be when you want to call your parent functions. If one class inherits another - it can override methods from the parent class, then call them using parent::function()