Accessing a not declared method in a class with php

Question

I am trying to understand this line of code:

$ret = $box->$command();

The method command is not defined in the class $box, and it is strange that there is a $ before command. I just don't get it.

Answer 1

$foo = 'bar';
$obj->$foo(); // calls the bar() method

You're looking at variable method calling.