Question

i was looking at a tutorial from ZendCasts where i wondered about the code he used. a simplified version below

class TestClass {
    private $_var;
    private static function getDefaultView() {
        if (self::$_var === null) { ... } // this is the line in question
    }
}

i wonder why is something like isset(self::$_var) not used instead?
when i use self:: i need the $ sign to refer to variables? i cant do self::_var?
how does == differ from ===

Answer 1

These are several questions.

I wonder why is something like isset(self::$_var) not used instead

It’s indifferent. The advantage of using isset is that a notice is not emitted if the variable ins’t defined. In that case, self::$_var is always defined because it’s a declared (non-dynamic) property. isset also returns false if the variable is null.

when i use self:: i need the $ sign to refer to variables?

Note that this is not a regular variable, it’s a class property (hence the self, which refers to the class of the method). Yes, except if this is a constant. E.g.:

class TestClass {
    const VAR;
    private static function foo() {
        echo self::VAR;
    }
}

how does == differ from ===

This has been asked multiple times in this site alone.