Strange Object/Class Issue (stdClass)

Question

I've just recently began messing around with anonymous functions, and I decided to try and put it to actual use in a larger project. After hitting a road block, I tried setting up a small practice script, but the same issue persists. I don't quite understand what's going on, but here's some code,

$a = function($in) {
  echo $in;
};
$a('b4ng');

The above works just fine, as does the following,

class Foo {

    public $cmd;

    public function __construct() {

        $this->cmd = new stdClass();
        $this->cmd->a = 'b4ng';
    }
}

$bar = new Foo();
echo $bar->cmd->a;

That being made clear, the following does not work,

class Foo {

    public $cmd;

    public function __construct() {

        $this->cmd = new stdClass();
        $this->cmd->message = function($in) {

            echo $in;
        };
    }
}

$bar = new Foo();
$bar->cmd->message('b4ng');

When attempting to use the snippet above, I'm hit with the following error,

Fatal error: Call to undefined method stdClass::message()

I understand what the error is telling me, I just don't understand why; 'message' obviously isn't a native function/method of stdClass, but it was declared in 'cmd'.

possible duplicate of Calling closure assigned to object property directly - $bar->cmd->message->__invoke('b4ng'); — FuzzyTree
– FuzzyTree, Commented Jul 19, 2014 at 4:09
@FuzzyTree, thank you, my apologies for not looking around prior to posting this question. In any case, my problem is solved. — user1117742456
– user1117742456, Commented Jul 19, 2014 at 4:16

Ulrich Eckhardt · Accepted Answer · 2014-07-19 09:09:48Z

1

There is another thing you can't do:

$o = new SomeClass();
$m = $o->someMethod;
$m();

The issue here is that PHP has a special syntax for a member function call, which is what matches $o->foo(). In your case though, foo is a closure (i.e. a data member, not a method) so that causes the error. In order to fix this, you first need to retrieve foo from your object and then invoke it:

// use brackets to force evaluation order
($o->foo)(args..);
// use dedicated function
call_user_func($o->foo, args..);
// use two steps
$foo = $o->foo;
$foo(args..);

I'd try the first variant first, but I'm not sure if PHP allows it. The last variant is the most cludgy, but that one surely works.

answered Jul 19, 2014 at 9:09

Ulrich Eckhardt

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elixenide · Accepted Answer · 2014-07-19 03:58:05Z

0

In PHP, you can't define class methods outside the class itself. So, you can't create an instance of stdClass and then dynamically create methods for it.

answered Jul 19, 2014 at 3:58

elixenide

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