PHP passing a class name becomes a string when passed to a function

Question

Here's what I want to do:

public function all($model) {
  $query = 'SELECT ' . implode(', ', $model::$fields) ....;
}

Called like this:

$thing->all(Account);

I get this error:

Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM in /home/mark/public_html/*/account.php on line 15

When inspecting $model with var_dump it turns out its a string. In the the first example if I change $model to Account on the $query line it works fine.

How can a take a string and turn it back into a class?

Edit: Updated example and title to reflect the problem isn't with self.

Solution: Since I'm not using PHP5.3, I had to resort to using eval() to get what I wanted. Thanks everybody!

Answer 1

Classes are not first-class citizens in PHP, as such they may not be stored in variables, passed as function arguments, or returned from functions.

However, PHP will let you simulate a first-class citizen by using a string containing the name of the class, in certain situations:

$class = "Account";

$instance = new $class(); // You can create instances

call_user_func(array($class, 'frobnicate')); // You can call static functions

That's about all in PHP < 5.3. However, with PHP 5.3, you can also:

$class::frobnicate(); // cleanly call static functions

$fields = $class::$fields; // access static variables

Answer 2

I have also experienced receiving such Fatal Error: Class 'MyClass' not found when you're class has a specific namespace, then it's probably the namespacing. You need to also mention the namespace in your String variable.

$class = "App\MyClass"; // mention the namespace too
$instance = new $class();