Is that a bug in stdClass?

Question

In PHP it is possible to declare a variable at the same time as we pass it as a function parameter or at class instantiation.

Let me give you an example with the function is_file and the class ArrayObject.

$arrayObject = new ArrayObject($a = []);

var_dump($a); // Imprime: array(0) {}


is_file($b = 'index.php');

print_r($b); // Imprime: "index.php";

But when we do it in stdClass, something unexpected happens.

$object = new stdClass($c = []);

print_r($c); //Undefined variable 'c'

Note: To prove I’m not making it up, here comes the code on IDEONE

Updating: Because the posted answers talk about have to do with the parameters in the class or function constructor, or not so that the assignment happens when we assign the value to a variable that at the same time we pass as parameter, I am putting an example code to prove that this is not true.

I created three scenarios.

• The first class ComParametro accepts only one parameter in the constructor
• The second class SemParametro does not accept any meter in the constructor, as in the case of stdClass
• And lastly, we have the stdClass.

Let’s see:

class ComParametro
{
   public function __construct($parametro){}
}


class SemParametro
{
    public function __construct(){}
}

new ComParametro($a = 'a');


print_r($a);

new SemParametro($b = 'b');

print_r($b);

new stdClass($c = 'c');

print_r($c);

As we can see in the IDEONE, the results were respectively:

a
b
Undefined variable 'c'

So what I want to know is why this behavior is present in stdClass!

Answer 1

I don’t know how PHP handles this case, but if a class has not defined the constructor (which is the case stdClass), then any assignment will be invalid at the time of the object instantiation.

Example

<?php
class aa {
  function __construct() {}
}

class bb {
}

new aa($a = []);

var_dump($a);

new bb($b = []);

var_dump($b);

Answer 2

stdClass does not accept parameters.

The best way to define a value like this for sdtClass is a conversion:

$std = (object)$c = [];

var_dump($std); // Retorna object(stdClass)#1 (0) {}
var_dump($c); // Retorna array(0) {}

So NO, this is the definition of the class and not a bug.

Answer 3

To further strengthen our theory regarding the question, I will give my opinion on the subject.

As exemplified by our friend, the question is not whether you have a constructor or function with or without parameters. This does not affect anything in relation to the variable passed by argument.

The examples below will cause the variables to be assigned:

function a(){}

class b
{
   public function __construct(){}
}

a($a = 1);
new b($b = 2);

var_dump($a, $b); // Imprime 1 e 2

In case the constructor is not defined, the problem described in the question occurs:

class C{}

new C($c = 3);

var_dump($c); // Undefined variable 'c'

This is a question that is probably related to the PHP interpreter. If the class has no constructor, then there is no need to process what is passed as class instance parameter - maybe they thought so when they did the encoding of the classes.

The last thing we have to do then is to check whether the stdClass really doesn’t own the __construct internally - only for concrete evidence.

So come on:

$object = new stdClass;

$reflector = new ReflectionClass($object);

var_dump($reflector->getConstructor()); // NULL

Already in ArrayObject

$reflector = new ReflectionClass(new ArrayObject());

var_dump($reflector->getConstructor());

The exit is :

class ReflectionMethod#4 (2) {
  public $name =>
  string(11) "__construct"
  public $class =>
  string(11) "ArrayObject"
}

Then it is proven that there is no __construct in class stdClass