I wanna call a Child Method in Main Class without declare new child();
class main {
function __construct() {
}
public function test() {
}
}
class child extends main {
function __construct() {
}
function childmethod() {
return "test";
}
}
$main = new main();
$main->childmethod();
best wishes
Make class as abstract and declare the method you want to call from child class as abstract.
abstract class main {
function __construct() {
}
public function test() {
return "test";
}
abstract function childmethod();
}
class child extends main {
function __construct() {
}
function childmethod() {
return "childmethod";
}
}
$main = new child();
echo $main->childmethod();// echoes childmethod
echo $main->test();// echoes test
If I correctly understand what you're asking for, you cannot do it and it's a mistake in the project idea.
If you need to call a child method in the parent, it means the method should go in the parent.
There's no way to call a method of an object without instantiate the object, unless you create a static method
Say I have class child() and class parent(). The parent has a constructor and a few other public methods, and the child is empty apart from a constructor.
How do I go about calling a parent's methods inside of the child's constructor, as in:
Class Parent {
public function __construct() {
// Do stuff (set up a db connection, for example)
}
public function run($someArgument) {
// Manipulation
return $modifiedArgument;
}
}
Class Child extends Parent {
public function __construct() {
// Access parent methods here?
}
}
Say I want to call parents run() method, do I have to call a new instance of the parent inside the child constructor? Like so...
$var = new Parent();
$var->run($someArgument);
If so, what is the point of extends from a class definition POV? I can call a new instance of another class with the new keyword whether it extends the 'child' or not.
My (likely) wrong understanding was that by using extends you can link classes and methods from a parent can be inherited into the child. Is that only outside the class definition? Does using extend offer no efficiencies inside the class definition?
Because referring to the parent's run() method with the this keyword certainly doesn't work...
Use parent as predefined reference: parent::run(). This will ensure you call parent method. The same way you could call first parent constructor first or after child one - parent::__construct().
Class Child extends Parent {
public function __construct() {
parent::__construct();
// Access parent methods here?
$some_arg = NULL; // init from constructor argument or somewhere else
parent::run($some_arg); // explicitly call parent method
// $this->run($some_arg); // implicitly will call parent if no child override
}
}
If you dont have an implementation in child you could call $this->run($args), where it will again call parent run method.
To extend Rolice's answer
function a() {
echo 'I exist everywhere';
}
class A {
protected $a
function a() {
$this->a = 'I have been called';
}
function out() {
echo $this->a;
a();
}
}
class B extends A {
function __construct() {
parent::a();// original method
$this->a(); // overridden method
a();
}
function a() {
$this->a = $this->a ? 'I have been overwritten' : 'first call';
}
}
Study these to understand the difference
My Class is independant from another Class.
Inside my Class, a function is doing the same but refined job as a function in another Class. Can I use parent:: function_in_another_class() and get my function join that parent funciton's job flow?
No.
In PHP you can only extend from none or one class. As you write both classes are independent to each other, there is no information where to find the one or the other class.
But what you're looking for is probably this:
class A
{
function myFunction() {}
}
class B
{
private $a;
public function __construct(A $a)
{
$this->a = $a;
}
public function myFunction()
{
$this->a->myFunction();
}
}
If any class method already doing the same thing why would you bother call join it?
You can not do it. If you want the same job flow best way to do is to instantiate the other class and invoke that very same method. Thats why we use OOP.
See the example,
interface Fable()
{
public function f();
}
class OtherClass implements Fable
{
public function f()
{
// job flow
}
}
class MyClass
{
private $fable;
public function __construct(Fable $f)
{
$this->fable = $f;
}
public function method1($args){
return $this->fable->f($args);
}
}
If the current class is a child of another class, yes, you can. parent references to the parent class.
From php.net:
<?php
class A {
function example() {
echo "I am A::example() and provide basic functionality.<br />\n";
}
}
class B extends A {
function example() {
echo "I am B::example() and provide additional functionality.<br />\n";
parent::example();
}
}
$b = new B;
// This will call B::example(), which will in turn call A::example().
$b->example();
?>
The best you can do here is to extend Class B from Class A
Class B extends Class A
But, you can also:
class ClassA {
function do_something($args) {
// Do something
}
}
class ClassB {
function do_something_inclassA($args) {
classA::do_something($args);
}
}
Important: calling classa::do_something(); is a static call, in other words with error reporting E_STRICT you will get a static notice warning because function do_something() is not static function do_something()
Also, calling this function statically (i.e. classa::do_something()) means that class a's function cannot refer to $this within it
I am trying to create a simple MVC my personal use and I could really use an answer to this simple question
class theParent extends grandParent{
protected $hello = "Hello World";
public function __construct() {
parent::__construct();
}
public function route_to($where) {
call_user_func(array("Child", $where), $this);
}
}
class Child extends theParent {
public function __construct() {
parent::__construct();
}
public function index($var) {
echo $this->hello;
}
}
$x = new theParent();
$x->route_to('index');
Now Child::index() this throws a fatal error: Using $this when not in object context but if I were to use echo $var->hello, it works just fine.
I know I can use $var to access all properties in the parent, but I would rather use $this.
By writing call_user_func(array("Child", $where), $this) you are calling the method statically. But as your method isn't static you need some kind of object instance:
call_user_func(array(new Child, $where), $this);
Documentation on callback functions.
You don't have an instance of Child to call a non-static method upon when you're doing $x->route_to('index'); The way you're calling the method, without having made an instance first, is implied static.
There are two ways to correct it. Either make the Child class's methods static:
class Child extends theParent {
public function __construct() {
parent::__construct();
}
static public function index($var) {
echo self::$hello;
}
}
...or make an instance of the child class for the parent to use:
class theParent extends grandParent{
protected $hello = "Hello World";
private $child = false
public function __construct() {
parent::__construct();
}
public function route_to($where) {
if ($this->child == false)
$this->child = new Child();
call_user_func(array($this->child, $where), $this);
}
}
Of course, both of these samples are rather generic and useless, but you see the concept at hand.
$this gives you access to everything visible/accessible in the current object. That can either be in the class itself (this) or any of it's parents public or protected members/functions.
In case the current class overrides something of a parent class, you can access the parent method explicitly using the parent keyword/label, whereas you add :: to it regardless if it is not a static method.
Protected variables exist only once, so you can not use parent to access them.
Is this info of use?
How do i call a function of a child class from parent class?
Consider this:
class whale
{
function __construct()
{
// some code here
}
function myfunc()
{
// how do i call the "test" function of fish class here??
}
}
class fish extends whale
{
function __construct()
{
parent::construct();
}
function test()
{
echo "So you managed to call me !!";
}
}
That's what abstract classes are for. An abstract class basically says: Whoever is inheriting from me, must have this function (or these functions).
abstract class whale
{
function __construct()
{
// some code here
}
function myfunc()
{
$this->test();
}
abstract function test();
}
class fish extends whale
{
function __construct()
{
parent::__construct();
}
function test()
{
echo "So you managed to call me !!";
}
}
$fish = new fish();
$fish->test();
$fish->myfunc();
Okay, this answer is VERY late, but why didn't anybody think of this?
Class A{
function call_child_method(){
if(method_exists($this, 'child_method')){
$this->child_method();
}
}
}
And the method is defined in the extending class:
Class B extends A{
function child_method(){
echo 'I am the child method!';
}
}
So with the following code:
$test = new B();
$test->call_child_method();
The output will be:
I am a child method!
I use this to call hook methods which can be defined by a child class but don't have to be.
Technically, you cannot call a fish instance (child) from a whale instance (parent), but since you are dealing with inheritance, myFunc() will be available in your fish instance anyway, so you can call $yourFishInstance->myFunc() directly.
If you are refering to the template method pattern, then just write $this->test() as the method body. Calling myFunc() from a fish instance will delegate the call to test() in the fish instance. But again, no calling from a whale instance to a fish instance.
On a sidenote, a whale is a mammal and not a fish ;)
Ok, well there are so many things wrong with this question I don't really know where to start.
Firstly, fish aren't whales and whales aren't fish. Whales are mammals.
Secondly, if you want to call a function in a child class from a parent class that doesn't exist in your parent class then your abstraction is seriously flawed and you should rethink it from scratch.
Third, in PHP you could just do:
function myfunc() {
$this->test();
}
In an instance of whale it will cause an error. In an instance of fish it should work.
Since PHP 5.3 you can use the static keyword to call a method from the called class. i.e.:
<?php
class A {
public static function who() {
echo __CLASS__;
}
public static function test() {
static::who(); // Here comes Late Static Bindings
}
}
class B extends A {
public static function who() {
echo __CLASS__;
}
}
B::test();
?>
The above example will output:
B
source: PHP.net / Late Static Bindings
I'd go with the abstract class....
but in PHP you don't have to use them to make it work. Even the invocation of the parent class' constructor is a "normal" method call and the object is fully "operational" at this point, i.e. $this "knows" about all the members, inherited or not.
class Foo
{
public function __construct() {
echo "Foo::__construct()\n";
$this->init();
}
}
class Bar extends Foo
{
public function __construct() {
echo "Bar::__construct()\n";
parent::__construct();
}
public function init() {
echo "Bar::init()\n";
}
}
$b = new Bar;
prints
Bar::__construct()
Foo::__construct()
Bar::init()
i.e. even though class Foo doesn't know anything about a function init() it can call the method since the lookup is based on what $this is a reference to.
That's the technical side. But you really should enforce the implementation of that method by either making it abstract (forcing descendants to implement it) or by providing a default implementation that can be overwritten.
I know this is probably a bit late for you, but I had to get around this problem as well. To help others understand why this is sometimes a requirement, here's my example:
I'm building an MVC framework for an application, I have a base controller class, which is extended by each individual controller class. Each controller will have different methods, depending on what the controller needs to do. Eg, mysite.com/event would load the event controller. mysite.com/event/create will load the event controller and call the 'create' method. In order to standardise the calling of the create function, we need the base controller class to access the methods of the child class, which will be different for every controller. So code-wise, we have the parent class:
class controller {
protected $aRequestBits;
public function __construct($urlSegments) {
array_shift($urlSegments);
$this->urlSegments = $urlSegments;
}
public function RunAction($child) {
$FunctionToRun = $this->urlSegments[0];
if(method_exists($child,$FunctionToRun)) {
$child->$FunctionToRun();
}
}
}
Then the child class:
class wordcontroller extends controller {
public function add() {
echo "Inside Add";
}
public function edit() {
echo "Inside Edit";
}
public function delete() {
echo "Inside Delete";
}
}
So the solution in my case was to pass the child instance itself back to the parent class as a parameter.
The only way you could do this would be through reflection. However, reflection is expensive and should only be used when necessary.
The true problem here is that a parent class should never rely on the existence of a child class method. This is a guiding principle of OOD, and indicates that there is a serious flaw in your design.
If your parent class is dependent on a specific child, then it cannot be used by any other child classes that might extend it as well. The parent-child relationship goes from abstraction to specificity, not the other way around. You would be much, much better off to put the required function in the parent class instead, and override it in the child classes if necessary. Something like this:
class whale
{
function myfunc()
{
echo "I am a ".get_class($this);
}
}
class fish extends whale
{
function myfunc()
{
echo "I am always a fish.";
}
}
It's very simple. You can do this without abstract class.
class whale
{
function __construct()
{
// some code here
}
/*
Child overridden this function, so child function will get called by parent.
I'm using this kind of techniques and working perfectly.
*/
function test(){
return "";
}
function myfunc()
{
$this->test();
}
}
class fish extends whale
{
function __construct()
{
parent::construct();
}
function test()
{
echo "So you managed to call me !!";
}
}
Even if this is an old question, this is my solution using ReflectionMethod:
class whale
{
function __construct()
{
// some code here
}
function myfunc()
{
//Get the class name
$name = get_called_class();
//Create a ReflectionMethod using the class and method name
$reflection = new \ReflectionMethod($class, 'test');
//Call the method
$reflection->invoke($this);
}
}
The benefit of using the ReflectionMethod class is that you could pass an array of arguments and check which one is needed in the method you are calling:
//Pass a list of arguments as an associative array
function myfunc($arguments){
//Get the class name
$name = get_called_class();
//Create a ReflectionMethod using the class and method name
$reflection = new \ReflectionMethod($class, 'test');
//Get a list of parameters
$parameters = $reflection->getParameters()
//Prepare argument list
$list = array();
foreach($parameters as $param){
//Get the argument name
$name = $param->getName();
if(!array_key_exists($name, $arguments) && !$param->isOptional())
throw new \BadMethodCallException(sprintf('Missing parameter %s in method %s::%s!', $name, $class, $method));
//Set parameter
$list[$name] = $arguments[$name];
}
//Call the method
$reflection->invokeArgs($this, $list);
}
From whale instance you can't call this function. but from fish instance you can do
function myfunc()
{
static::test();
}
If exists a method in the child class, method will be called from the parent class (as an optional callback if exists)
<?php
class controller
{
public function saveChanges($data)
{
//save changes code
// Insert, update ... after ... check if exists callback
if (method_exists($this, 'saveChangesCallback')) {
$arguments = array('data' => $data);
call_user_func_array(array($this, 'saveChangesCallback'), $arguments);
}
}
}
class mycontroller extends controller
{
public function setData($data)
{
// Call parent::saveChanges
$this->saveChanges($data);
}
public function saveChangesCallback($data)
{
//after parent::saveChanges call, this function will be called if exists on this child
// This will show data and all methods called by chronological order:
var_dump($data);
echo "<br><br><b>Steps:</b><pre>";
print_r(array_reverse(debug_backtrace()));
echo "</pre>";
}
}
$mycontroller = new mycontroller();
$mycontroller->setData(array('code' => 1, 'description' => 'Example'));
That's a little tricky
if you talk about OOP concepts that's not possible
but if you use your brain then it can be :)
OOP say's you cannot call child class function from parent class and that's correct because inheritance is made of inheriting parent functions in child
but
you can achieve this with Static class
class Parent
{
static function test()
{
HelperThread::$tempClass::useMe();
}
}
class child extends parent
{
// you need to call this. functon everytime you want to use
static function init()
{
HelperThread::$tempClass = self::class;
}
static function useMe()
{
echo "Ahh. thank God you manage a way to use me";
}
}
class HelperThread
{
public static $tempClass;
}
that's just a solution to my problem.
i hope it helps with your problem
Happy Coding :)
what if whale isn't extended? what would that function call result in? Unfortunately there is no way to do it.
Oh, and does a fish extend a whale? A fish is a fish, a whale is a mammal.