Question

When using OOP in PHP I’ve seen a lot of functions written like this: function __myfunc(){}
I want to know what the underscores do. I’ve read they protect the function but from what and how?

Another example:

class myClass{
    function __myFunc(){
        return ' what am i doing?';
    }
}
$question = new myClass;
echo $question->__myFunc();

Answer 1

The underscores have no effect. However, two underscores are used to indicate a magic function that has special meaning, e.g. the constructor __construct() or the destructor __destruct(). Some people used one or two underscores to indicate that a method is meant to be “private”, i.e. used only internally. Since this feature is implemented in PHP >= 5 as a special keyword, you shouldn’t use this “underscoring” anymore:

class myClass{
    private function myFunc() {
        return ' what am i doing?';
    }
}

$question = new myClass();
echo $question->myFunc(); // fails!