Is it possible to use class as variable in PHP? - php

I have a class as follows:
class Integer {
private $variable;
public function __construct($variable) {
$this->varaible = $variable;
}
// Works with string only
public function __isString() {
return $this->variable;
}
// Works only, If Im using the class as a function (i must use parenthesis)
public function __invoke() {
return $this->variable;
}
}
$int = new Integer($variable);
I would like work with class as with variable like:
$result = $int + 10;
I donĀ“t known, how can I return $int; ?

PHP does not support overloading operators (which is the technical thing you're looking for). It doesn't know what to do with + when one of the operands is a class Integer, and there's no way to teach PHP what to do. The best you can do is implement appropriate methods:
class Integer {
..
public function add(Integer $int) {
return new Integer($this->variable + $int->variable);
}
}
$a = new Integer(1);
$b = new Integer(2);
echo $a->add($b);

Yes, see Example 4 of php's call_users_func() page;
<?php
class myclass {
static function say_hello()
{
echo "Hello!\n";
}
}
$classname = "myclass";
call_user_func(array($classname, 'say_hello'));
call_user_func($classname .'::say_hello'); // As of 5.2.3
$myobject = new myclass();
call_user_func(array($myobject, 'say_hello'));
?>

public function __construct($variable) {
$this->varaible = $variable;
}
are this typo or not? on $this->varaible ?

Related

Auto-check equality of two objects?

I need to check if two PHP object are equal in terms of equal values. Of course I could easily add an isEqualTo(...) method to the class that compares all relevant values. However the concrete class will change in the near future and I would like to know if there is any automated way to do this.
Example:
class Contact {
private name; // String
private phone; // Int
private someObject; // Custom Object
public function getName() {
return $this->name;
}
public function setName($newName) {
$this->name = $newName;
}
public function getPhone() {
return $this->phone;
}
public function setPhone($newPhone) {
$this->phone = $newPhone;
}
public function getSomeObject() {
return $this->someObject;
}
public function setSomeObject($newObj) {
$this->someObject = $newObj;
}
// Manual Solution
public function isEqualTo($contact) {
result = $this->name == $contact->getName();
result &= $this->phone == $contact->getPhone();
result &= $this->someObject == $contact->getSomeObject();
return result;
}
}
This would obviously work. Of course I am aware of the the limitation of comparing someObject (need to be the exact some object to be true) but this is OK.
However the class Contact will be extended in the near future. Everytime I add new properties/values to the class I have to add them to isEqualTo as well. No big deal but a little bit cumbersome.
So, is there any way to implement isEqualTo to automatically all available public properties?
I found get_class_vars and get_object_vars but these methodes will not work with getters and setters but only with vars that can be accessed directly.
I found get_class_methodes but this return all methodes and not only getters and setters. Filtering the methodes names by get... and set... would work of course, but this would be more like a hack than a "nice and clean" soltution.
In short: Is there any "correct" way to automatically check two PHP object for equality?
I wouldn't go so far as to say that this is the "correct" way, but since you don't want to implement/maintain your own comparison function/method you might be interested in php's default behaviour including the comparison of protected/private properties:
<?php
class Foo {
private $x,$y,$z;
public function __construct($x,$y,$z) {
$this->x = $x;
$this->y = $y;
$this->z = $z;
}
}
$f1 = new Foo(1,2,3);
$f2 = new Foo(4,5,6);
$f3 = new Foo(1,2,3);
var_dump(
$f1==$f2,
$f1==$f3
);
prints
bool(false)
bool(true)
which might or might not be sufficient for you.
As pointed out by Alma Do, circular references like e.g.
<?php
class Foo {
private $x,$y,$z;
public function __construct($x,$y,$z) {
$this->x = $x;
$this->y = $y;
$this->z = $z;
}
public function setZ($z) {
$this->z = $z;
}
}
$f1 = new Foo(1,2,3);
$f2 = new Foo(4,5,6);
$f3 = new Foo(1,2,3);
$f1->setZ($f3);
$f3->setZ($f1);
var_dump(
$f1==$f2,
$f1==$f3
);
will cause a Fatal error: Nesting level too deep - recursive dependency?.
You could use Reflection to do this, but i don't think it's a good idea. Maybe serialize() is a better solution?
function isEquals(self $obj){
return serialize($obj)===serialize($this)
}

Class variables holding a function in PHP

PHP allows for variables to hold functions like so:
$f = function($a,$b) {
print "$a $b";
};
$f("Hello","World!"); //prints 'Hello World!'
This works just fine for me. I'm trying to pass a function into a class and set an instance variable to hold that function but with little luck:
class Clusterer {
private $distanceFunc;
public function __construct($f) {
$this->distanceFunc = $f;
print $f(1,7); //works
print $this->distanceFunc(1,7); //exceptions and errors abound
}
}
$func = function($a,$b) {
return abs($a-$b);
}
$c = new Clusterer($func);
Am I doing something wrong here? The error is that the function doesn't exist so my guess currently is that it looks for a class function with that name (which there isn't one) and then gives up rather than looking for variables as well... how can I make it view the $this->distanceFunc as a variable?
EDIT:
So after the advice from the answers below, I found a solution which was the make a function to wrap the invocation. For example my class is now:
class Clusterer {
private $distanceFunc;
public function __construct($f) {
$this->distanceFunc = $f;
print $f(1,7); //works
print $this->distanceFunc(1,7); //exceptions and errors abound
}
private function distanceFunc($a,$b) {
$holder = $this->distanceFunc;
return $holder($a,$b);
}
}
$func = function($a,$b) {
return abs($a-$b);
}
$c = new Clusterer($func);
and this works great. Php looks for functions first and can only tell if it is a variable by context I guess is the moral of this story.
Your code doesn't work because PHP interprets $this->distanceFunc(1,7) as a class method, but you can do the following:
class Clusterer {
private $distanceFunc;
public function __construct($f) {
$this->distanceFunc = $f;
print $f(1,7); //works
print call_user_func_array($this->distanceFunc, array(1, 7));
// print $this->distanceFunc(1,7); //exceptions and errors abound
}
}
$func = function($a,$b) {
return abs($a-$b);
};
$c = new Clusterer($func);
http://sandbox.onlinephpfunctions.com/code/cdc1bd6bd50f62d5c88631387ac9543368069310
In PHP, methods and properties of an object occupy separate namespaces. This is different from JavaScript, for example, where foo.bar = function() {} is a perfectly valid way of defining a method.
Consequently, $this->distanceFunc(1,7); looks for a method named distanceFunc on the current class, and the classes it inherits from, but never looks for the property which you happen to have given the same name.
One solution is to force PHP to look up a property, then execute it, e.g. $foo = $this->distanceFunc; $foo(1,7) or call_user_func($this->distanceFunc, 1, 7)
Another would be to define the magic method __call on your class, which gets run whenever a non-existent method is referenced. Something like this ought to work (I don't have an easy way to testright now):
function __call($func, $args) {
if ( property_exists($this, $func) && is_callable($this->$func) ) {
return call_user_func_array($this->$func, $args);
}
}
Note that this still isn't the same as a real method, for instance in terms of access to private properties.
It looks like you're going for a strategy pattern here. IE you want to be able to inject different methods for calculating distance? If so there is a more "sane" way to do it.
You can define an interface to the classes you will use to store the strategy method ensuring that the class will always have the method calculate() for example which would be your distance calculation function. Then in the constructor of your Clusterer class, type check against the interface in the parameter and call calculate() on the object passed in.
Looks like this:
interface Calculateable
{
public function calculate();
}
class MyDistanceCalculator implements Calculateable
{
public function calculate()
{
// Your function here
}
}
class Clusterer
{
protected $calc;
public function __construct(Calculateable $calc)
{
$this->calc = $calc;
$this->calc->calculate();
}
}
$myClusterer = new Clusterer(new MyDistanceCalculator());
Because you defined an interface, any object you pass in will have the calculate() function
In HHVM, you can do this:
<?php
class Foo
{
public function __construct()
{
$this->bar = function() { echo "Here\n"; };
($this->bar)();
}
}
new Foo();
But it's not yet supported in PHP. But, it will be in PHP 7 (there will be no release named PHP 6).
PHP doesn't have first class functions. In JavaScript if you returned a function you could do this: myFunctionThatReturnsAFunction()(1,2), but not in PHP.
<?php
class Clusterer {
private $distanceFunc;
public function __construct(Closure $f) {
$this->distanceFunc = $f;
}
public function getDistFunc()
{
return $this->distanceFunc;
}
}
$func = function($a,$b) {
return abs($a-$b);
};
$c = new Clusterer($func);
$a = $c->getDistFunc();
echo $a(1,2);
Take a look at call_user_func
class Clusterer {
private $distanceFunc;
public function __construct($f) {
$this->distanceFunc = $f;
print $f(1,7); //works
print call_user_func($this->distanceFunc, 1, 7); //works too ;)
}
}
$func = function($a,$b) {
return abs($a-$b);
};
$c = new Clusterer($func);
Don't ask me what is the difference, but it works the way you want (One of the reasons i hate this language)

PHP dynamic class extending

I know you can extend a class when constructing it like the following:
class b extends a {
}
But is it possible to dynamically extend classes from the scripts? Such as:
$b = new b($input) extends a;
What I wish to accomplish is to extend the module differnetly wheither it's used in admin rather than the public pages. I know I can create two different parent classes by the same name and only include one per admin or public. But my question is, is it possible to do it dynamically in PHP?
No, not without an extension like RunKit.
You might consider an alternative approach. If you want B to assume the functionality of A, perhaps something like the following could provide a sort of "mixin" approach. The general picture is that, instead of B being a child of A, B delegates to A.
<?php
class MixMeIn
{
public $favouriteNumber = 7;
public function sayHi() {
echo "Hello\n";
}
}
class BoringClass
{
private $mixins = array();
public function mixin($object)
{
$this->mixins[] = $object;
}
public function doNothing() {
echo "Zzz\n";
}
public function __call($method, $args)
{
foreach ($this->mixins as $mixin)
{
if (method_exists($mixin, $method))
{
return call_user_func_array(array($mixin, $method), $args);
}
}
throw new Exception(__CLASS__ + " has no method " + $method);
}
public function __get($attr)
{
foreach ($this->mixins as $mixin)
{
if (property_exists($mixin, $attr))
{
return $mixin->$attr;
}
}
throw new Exception(__CLASS__ + " has no property " + $attr);
}
public function __set($attr, $value)
{
foreach ($this->mixins as $mixin)
{
if (property_exists($mixin, $attr))
{
return $mixin->$attr = $value;
}
}
throw new Exception(__CLASS__ + " has no property " + $attr);
}
}
// testing
$boring = new BoringClass();
$boring->doNothing();
try {
$boring->sayHi(); // not available :-(
}
catch (Exception $e) {
echo "sayHi didn't work: ", $e->getMessage(), "\n";
}
// now we mixin the fun stuff!
$boring->mixin(new MixMeIn());
$boring->sayHi(); // works! :-)
echo $boring->favouriteNumber;
Just a zany idea. I hope I understood the question correctly.
You can't, but this has been requested for a few years: https://bugs.php.net/bug.php?id=41856&edit=1
You can define the classes within an eval, but it's more trouble than declaring the class normally.
But you cannot use extends while object creation. extends is used in class definition only and defines which other class is "parent" for our new class.
Alternatively, if you are comfortable with javascript-style inheritance and don't mind losing typechecking:
<? //PHP 5.4+
final class ExpandoLookalike {
//Allow callable properties to be executed
public function __call($name, $arguments) {
\call_user_func_array($this->$name, $arguments);
}
}
$newBaseModule = static function(){
$base = new ExpandoLookalike();
//Common base functions get assigned here.
$basePrivateVar = 42;
$base->commonFunction = static function($params1, $params2) use ($basePrivateVar){
echo "common function\n";
};
$base->comment = static function() use ($basePrivateVar){
echo "Doing base comment with $basePrivateVar\n";
};
return $base;
};
//Javascript-style extends
$newAdminModule = static function($param) use ($newBaseModule){
$base = $newBaseModule();
$privateVar = 5;
$base->adminProperty = 60;
$base->suspendSite = static function() use ($param, $privateVar){
echo 'Doing admin only function ';
echo "with $param, $privateVar\n";
};
return $base;
};
$newPublicModule = static function() use ($newBaseModule){
$base = $newBaseModule();
$privateVar = 3;
//Javascript-style overloading
$oldComment = $base->comment;
$base->comment = static function($data) use ($oldComment, $privateVar){
$oldComment();
echo 'Doing public function ';
echo "with $data\n";
};
return $base;
};
$baseModule = $newBaseModule();
$adminModule = $newAdminModule('P');
$publicModule = $newPublicModule();
$adminModule->suspendSite(); //echos 'Doing admin only function with P, 5'
echo "{$adminModule->adminProperty}\n"; //echos '60'
$publicModule->comment('com'); //echos 'Doing base comment with 42'
//'Doing public function with com'
?>
Despite closing the door to traits and interfaces, it opens up other interesting doors to compensate:
<? //PHP 5.4+
$inheritAllTheThings = static function(){
$base = new ExpandoLookalike();
foreach(\func_get_args() as $object){
foreach($object as $key => $value){
//Properties from later objects overwrite properties from earlier ones.
$base->$key = $value;
}
}
return $base;
};
$allOfEm = $inheritAllTheThings(
$newPublicModule(),
$newAdminModule('Q'),
['anotherProp' => 69,]
);
$allOfEm->comment('f'); //echos 'Doing base comment with 42'
//Because AdminModule came after PublicModule, the function that echos 'f'
//from PublicModule was overridden by the function from AdminModule.
//Hence, order denotes resolutions for multiple inheritance collisions.
$allOfEm->suspendSite(); //echos 'Doing admin only function with Q, 5'
echo $allOfEm->anotherProp . "\n"; //echos '69'
?>
You can with typecasting. If a extends b then you could do
$a=(a)(new b($input));
Which isn't exactly the same, but similar.
You can look: https://github.com/ptrofimov/jslikeobject
Author implemented JS-like objects with support of inheritance.
But perhaps it is not so good to use such objects instead of usual ones.
Yes, as cory mentioned, this feature has been requested before. But before that, you can create a workaround. Here is my old school trick for this
Create two separate classes like these:
class a {
}
class b {
public $object;
}
Then, create an extended version too
class bextendeda extends a {
}
In the constructor method of class b, place few functions which redirects to the extended object if requested.
class b {
public $object;
public function __contruct($extend = false) {
if($extend) $this -> object = new bextendeda();
else $this -> object = $this;
}
function __get($prop) {
return $this-> object -> $prop;
}
function __set($prop, $val) {
$this-> object -> $prop = $val;
}
function __call($name, $arguments)
{
return call_user_func_array(array($this -> object, $name), $arguments);
}
}
And there you have it, IF you want the extended version just do this
$b = new b(true);
If not
$b = new b();
Enjoy :)

Why can't I overload constructors in PHP?

I have abandoned all hope of ever being able to overload my constructors in PHP, so what I'd really like to know is why.
Is there even a reason for it? Does it create inherently bad code? Is it widely accepted language design to not allow it, or are other languages nicer than PHP?
You can't overload ANY method in PHP. If you want to be able to instantiate a PHP object while passing several different combinations of parameters, use the factory pattern with a private constructor.
For example:
public MyClass {
private function __construct() {
...
}
public static function makeNewWithParameterA($paramA) {
$obj = new MyClass();
// other initialization
return $obj;
}
public static function makeNewWithParametersBandC($paramB, $paramC) {
$obj = new MyClass();
// other initialization
return $obj;
}
}
$myObject = MyClass::makeNewWithParameterA("foo");
$anotherObject = MyClass::makeNewWithParametersBandC("bar", 3);
You can use variable arguments to produce the same effect. Without strong typing, it doesn't make much sense to add, given default arguments and all of the other "work arounds."
For completeness, I'll suggest Fluent Interfaces. The idea is that by adding return $this; to the end of your methods you can chain calls together. So instead of
$car1 = new Car('blue', 'RWD');
$car2 = new Car('Ford', '300hp');
(which simply wouldn't work), you can do:
$car = (new Car)
->setColor('blue')
->setMake('Ford')
->setDrive('FWD');
That way you can pick exactly which properties you want to set. In a lot of ways it's similar to passing in an array of options to your initial call:
$car = new Car(['make' => 'Ford', 'seats' => 5]);
PHP Manual: Function Arguments, Default Values
I have overcome this simply by using default values for function parameters. In __constuct, list the required parameters first. List the optional parameters after that in the general form $param = null.
class User
{
private $db;
private $userInput;
public function __construct(Database $db, array $userInput = null)
{
$this->db = $db;
$this->userInput = $userInput;
}
}
This can be instantiated as:
$user = new User($db)
or
$user = new User($db, $inputArray);
This is not a perfect solution, but I have made this work by separating parameters into absolutely mandatory parameters no matter when the object is constructed, and, as a group, optional parameters listed in order of importance.
It works.
True overloading is indeed unsupported in PHP. As #Pestilence mentioned, you can use variable arguments. Some people just use an Associative Array of various options to overcome this.
they say this work:
<?php
class A
{
function __construct()
{
$a = func_get_args();
$i = func_num_args();
if (method_exists($this,$f='__construct'.$i)) {
call_user_func_array(array($this,$f),$a);
}
}
function __construct1($a1)
{
echo('__construct with 1 param called: '.$a1.PHP_EOL);
}
function __construct2($a1,$a2)
{
echo('__construct with 2 params called: '.$a1.','.$a2.PHP_EOL);
}
function __construct3($a1,$a2,$a3)
{
echo('__construct with 3 params called: '.$a1.','.$a2.','.$a3.PHP_EOL);
}
}
$o = new A('sheep');
$o = new A('sheep','cat');
$o = new A('sheep','cat','dog');
// results:
// __construct with 1 param called: sheep
// __construct with 2 params called: sheep,cat
// __construct with 3 params called: sheep,cat,dog
?>
and, it seem every one are happy with it, but for me it didn't work...
if you get it to work, its one kind of overloading too...
it take all argoments and pass them to the secondary function constructor...
<?php
//php do not automatically call parent class constructor at all if child class has constructor so you have to call parent class constructor explicitly, however parent class constructor is called automatically if child class has no constructor
class MyClass
{
function construct1($value1)
{
echo "<br/> dummy constructor is called with 1 arguments and it is $value1";
}
function construct2($value1,$value2)
{
echo "<br/> dummy constructor is called with 2 arguments and it is $value1, $value2";
}
function construct3($value1,$value2,$value3)
{
echo "<br/> dummy constructor is called with 3 arguments and it is $value1, $value2 , $value3";
}
public function __construct()
{
$NoOfArguments = func_num_args(); //return no of arguments passed in function
$arguments = func_get_args();
echo "<br/> child constructor is called $NoOfArguments";
switch ($NoOfArguments) {
case 1:
self::construct1($arguments[0]);
break;
case 2:
self::construct2($arguments[0],$arguments[1]);
break;
case 3:
self::construct3($arguments[0],$arguments[1],$arguments[2]);
break;
default:
echo "Invalid No of arguments passed";
break;
}
}
}
$c = new MyClass();
$c2 = new MyClass("ankit");
$c2 = new MyClass("ankit","Jiya");
$c2 = new MyClass("ankit","Jiya","Kasish");
?>
You can use conditional statements in your constructor and then perform your task.
Eg.
class Example
{
function __construct($no_of_args)
{// lets assume 2
switch($no_of_args)
{
case 1:
// write your code
break;
case 2:
//write your 2nd set of code
break;
default:
//write your default statement
}
}
}
$object1 = new Example(1); // this will run your 1st case
$object2 = new Example(2); // this will run your 2nd case
and so on...
You can of course overload any function in PHP using __call() and __callStatic() magic methods.
It is a little bit tricky, but the implementation can do exactly what your are looking for.
Here is the resource on the official PHP.net website:
https://www.php.net/manual/en/language.oop5.overloading.php#object.call
And here is the example which works for both static and non-static methods:
class MethodTest
{
public function __call($name, $arguments)
{
// Note: value of $name is case sensitive.
echo "Calling object method '$name' "
. implode(', ', $arguments). "\n";
}
/** As of PHP 5.3.0 */
public static function __callStatic($name, $arguments)
{
// Note: value of $name is case sensitive.
echo "Calling static method '$name' "
. implode(', ', $arguments). "\n";
}
}
$obj = new MethodTest;
$obj->runTest('in object context');
MethodTest::runTest('in static context'); // As of PHP 5.3.0
And you can apply this to constructors by using the following code in the __construct():
$clsName = get_class($this);
$clsName->methodName($args);
Pretty easy.
And you may want to implement __clone() to make a clone copy of the class with the method that you called without having the function that you called in every instance...
Adding this answer for completeness with respect to current PHP , since later versions of PHP , you can in fact overload constructors in a way . Following code will help to understand ,
<?php
class A
{
function __construct()
{
$a = func_get_args();
$i = func_num_args();
if (method_exists($this,$f='__construct'.$i)) {
call_user_func_array(array($this,$f),$a);
}
}
function __construct1($a1)
{
echo('__construct with 1 param called: '.$a1.PHP_EOL);
}
function __construct2($a1,$a2)
{
echo('__construct with 2 params called: '.$a1.','.$a2.PHP_EOL);
}
function __construct3($a1,$a2,$a3)
{
echo('__construct with 3 params called: '.$a1.','.$a2.','.$a3.PHP_EOL);
}
}
$o = new A('sheep');
$o = new A('sheep','cat');
$o = new A('sheep','cat','dog');
?>
Output :
__construct with 1 param called: sheep
__construct with 2 params called: sheep,cat
__construct with 3 params called: sheep,cat,dog
In this case I recommend using Interfaces:
interface IExample {
public function someMethod();
}
class oneParamConstructor implements IExample {
public function __construct(private int $someNumber) {
}
public function someMethod(){
}
}
class twoParamConstructor implements IExample {
public function __construct(private int $someNumber, string $someString) {
}
public function someMethod(){
}
}
than in your code:
function doSomething(IExample $example) {
$example->someMethod();
}
$a = new oneParamConstructor(12);
$b = new twoParamConstructor(45, "foo");
doSomething($a)
doSomething($b)
As far as I know, constructor overloading in PHP is not allowed, simply because the developers of PHP did not include that functionality - this is one of the many complaints about PHP.
I've heard of tricks and workarounds, but true overloading in the OOP sense is missing. Maybe in future versions, it will be included.
I think we can also use constructor with default arguments as a potential substitute to constructor overloading in PHP.
Still, it is really sad that true constructor overloading is not supported in PHP.
<?php
class myClass {
public $param1 = 'a';
public $param2 = 'b';
public function __construct($param1 = NULL, $param2 = NULL) {
if ($param1 == NULL && $param2 == NULL) {
// $this->param1 = $param1;
// $this->param2 = $param2;
} elseif ($param1 == NULL && $param2 !== NULL) {
// $this->param1 = $param1;
$this->param2 = $param2;
} elseif ($param1 !== NULL && $param2 == NULL) {
$this->param1 = $param1;
// $this->param2 = $param2;
} else {
$this->param1 = $param1;
$this->param2 = $param2;
}
}
}
// $myObject = new myClass();
// $myObject = new myClass(NULL, 2);
$myObject = new myClass(1, '');
// $myObject = new myClass(1, 2);
echo $myObject->param1;
echo "<br />";
echo $myObject->param2;
?>
public function construct1($user , $company)
{
dd("constructor 1");
$this->user = $user;
$this->company = $company;
}
public function construct2($cc_mail , $bcc_mail , $mail_data,$user,$company)
{
dd('constructor 2');
$this->mail_data=$mail_data;
$this->user=$user;
$this->company=$company;
$this->cc_mail=$cc_mail;
$this->bcc_mail=$bcc_mail;
}
public function __construct()
{
$NoOfArguments = func_num_args(); //return no of arguments passed in function
$arguments = func_get_args();
switch ($NoOfArguments) {
case 1:
self::construct1($arguments[0]);
break;
case 5:
self::construct2($arguments[0],$arguments[1],$arguments[2],$arguments[3],$arguments[4]);
break;
default:
echo "Invalid No of arguments passed";
break;
}
I'm really no OOP expert, but as I understand it overloading means the ability of a method to act differently depending in the parameters it receives as input. This is very much possible with PHP, you just don't declare the input types since PHP does not have strong typing, and all the overloading is done at runtime instead of compile time.

Reference to static method in PHP?

In PHP, I am able to use a normal function as a variable without problem, but I haven't figured out how to use a static method. Am I just missing the right syntax, or is this not possible?
(EDIT: the first suggested answer does not seem to work. I've extended my example to show the errors returned.)
function foo1($a,$b) { return $a/$b; }
class Bar
{
static function foo2($a,$b) { return $a/$b; }
public function UseReferences()
{
// WORKS FINE:
$fn = foo1;
print $fn(1,1);
// WORKS FINE:
print self::foo2(2,1);
print Bar::foo2(3,1);
// DOES NOT WORK ... error: Undefined class constant 'foo2'
//$fn = self::foo2;
//print $fn(4,1);
// DOES NOT WORK ... error: Call to undefined function self::foo2()
//$fn = 'self::foo2';
//print $fn(5,1);
// DOES NOT WORK ... error: Call to undefined function Bar::foo2()
//$fn = 'Bar::foo2';
//print $fn(5,1);
}
}
$x = new Bar();
$x->UseReferences();
(I am using PHP v5.2.6 -- does the answer change depending on version too?)
PHP handles callbacks as strings, not function pointers. The reason your first test works is because the PHP interpreter assumes foo1 as a string. If you have E_NOTICE level error enabled, you should see proof of that.
"Use of undefined constant foo1 - assumed 'foo1'"
You can't call static methods this way, unfortunately. The scope (class) is relevant so you need to use call_user_func instead.
<?php
function foo1($a,$b) { return $a/$b; }
class Bar
{
public static function foo2($a,$b) { return $a/$b; }
public function UseReferences()
{
$fn = 'foo1';
echo $fn(6,3);
$fn = array( 'self', 'foo2' );
print call_user_func( $fn, 6, 2 );
}
}
$b = new Bar;
$b->UseReferences();
In php 5.2, you can use a variable as the method name in a static call, but to use a variable as the class name, you'll have to use callbacks as described by BaileyP.
However, from php 5.3, you can use a variable as the class name in a static call. So:
class Bar
{
public static function foo2($a,$b) { return $a/$b; }
public function UseReferences()
{
$method = 'foo2';
print Bar::$method(6,2); // works in php 5.2.6
$class = 'Bar';
print $class::$method(6,2); // works in php 5.3
}
}
$b = new Bar;
$b->UseReferences();
?>
You could use the full name of static method, including the namespace.
<?php
function foo($method)
{
return $method('argument');
}
foo('YourClass::staticMethod');
foo('Namespace\YourClass::staticMethod');
The name array array('YourClass', 'staticMethod') is equal to it. But I think the string may be more clear for reading.
In PHP 5.3.0, you could also do the following:
<?php
class Foo {
static function Bar($a, $b) {
if ($a == $b)
return 0;
return ($a < $b) ? -1 : 1;
}
function RBar($a, $b) {
if ($a == $b)
return 0;
return ($a < $b) ? 1 : -1;
}
}
$vals = array(3,2,6,4,1);
$cmpFunc = array('Foo', 'Bar');
usort($vals, $cmpFunc);
// This would also work:
$fooInstance = new Foo();
$cmpFunc = array('fooInstance', 'RBar');
// Or
// $cmpFunc = array('fooInstance', 'Bar');
usort($vals, $cmpFunc);
?>
Coming from a javascript background and being spoiled by it, I just coded this:
function staticFunctionReference($name)
{
return function() use ($name)
{
$className = strstr($name, '::', true);
if (class_exists(__NAMESPACE__."\\$className")) $name = __NAMESPACE__."\\$name";
return call_user_func_array($name, func_get_args());
};
}
To use it:
$foo = staticFunctionReference('Foo::bar');
$foo('some', 'parameters');
It's a function that returns a function that calls the function you wanted to call. Sounds fancy but as you can see in practice it's piece of cake.
Works with namespaces and the returned function should work just like the static method - parameters work the same.
This seems to work for me:
<?php
class Foo{
static function Calc($x,$y){
return $x + $y;
}
public function Test(){
$z = self::Calc(3,4);
echo("z = ".$z);
}
}
$foo = new Foo();
$foo->Test();
?>
In addition to what was said you can also use PHP's reflection capabilities:
class Bar {
public static function foo($foo, $bar) {
return $foo . ' ' . $bar;
}
public function useReferences () {
$method = new ReflectionMethod($this, 'foo');
// Note NULL as the first argument for a static call
$result = $method->invoke(NULL, '123', 'xyz');
}
}
"A member or method declared with static can not be accessed with a variable that is an instance of the object and cannot be re-defined in an extending class"
(http://theserverpages.com/php/manual/en/language.oop5.static.php)

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