CODEWITHSUNDEEP
php
imkingdavid
imkingdavid

Reputation: 1389

What is returned? (Class method access on instantiation)

EDIT: Please note that I am appending my original question with my actual question due to realizing that I asked the wrong question (by forgetting what I actually meant to ask).

In PHP 5.4 (as of RC1), it is possible to access class methods on class instantiation.

In other words, as I understand it, it is now possible to do: $foo = new bar()->foobar(); which saves times and lines of code.

For my question, let's look at the following example:

class foo {
    function __construct() {
    }

    function bar() {
        return 'world';
    }
}

$foobar = (new foo())->bar();
echo $foobar;

My question is, in such a case, when both the constructor and the method that is called upon initialization return a value, what is output by the final line (i.e. echo $foobar;)?

If I had to guess, since I haven't actually had a chance to play around with 5.4 yet, the return from foo::bar() would overwrite the return from foo::__construct() because it is returned last. But I just wanted to check.

Okay, so the above question is not even logical (since __construct() should not return). What I really meant to ask is this: Does $foobar in the above example contain the class instance or the return from $bar? If the latter, what sense does it make to use this if the class will not be available after instantiated? Wouldn't it be better to just use a static method or call the method on its own line?

Upvotes: 0

Views: 114

Answers (2)

hakre
hakre

Reputation: 198237

Your example is missing parenthesis:

$foobar = (new foo())->bar();
echo $foobar; # world

Because __construct() returns nothing, the return statement is useless inside the constructor. That was possible in PHP 4 IIRC, but since PHP 5 new will always return the object.

Edit:

Does $foobar in the above example contain the class instance or the return from $[sic!]bar[()]?

The return value (if you fix the parenthesis). So the latter.

If the latter, what sense does it make to use this if the class will not be available after instantiated?

What makes sense or not is in the eye of the beholder. Normally you can not look into classes, so, expect that a class method needs the object.

Wouldn't it be better to just use a static method or call the method on its own line?

Calling a static function is not the same as calling an object method. For example, the method might not work when called statically.

Writing the method call on it's own line is generally considered good practice because it's better readable:

$foo = new foo();
echo $foo->bar();

Upvotes: 0

Mathieu Dumoulin
Mathieu Dumoulin

Reputation: 12244

First of all, you should never return anything from a constructor. Thats a basic rule. Now some of us don't follow this because they like the concept of calling their constructor afterwards and receiving some input instead of nothing.

But in the case of a good programming strategy, a constructor should be called only via the "new" keyword and shouldn't return anything.

And yes, in all cases, NEW CLASSNAME() returns the instanciated object in all cases :)

Happy programming...

<?php
class myclass {
        public function __construct(){
                return 'hello';
        }
}

$a = new myclass();
var_dump($a);
var_dump($a->__construct());

Will output

object(myclass)#1 (0) { } 
string(5) "hello"

EDIT following question change

My educated guess is that $foobar will contain "world" and thus echo it with your code.

Same thing occurs in other languages such as in c#. You can instanciate an object call a method directly inline and lose the object only to get the return from the inline function called.

var_dump(new foo()); //Will var_dump the object
var_dump(new foo()->bar()); //Will var_dump "world"

Upvotes: 1

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