Why should I initialize variables in a class?

Question

Why do I have to initialize variables in a class?

$test = new myclass();
class myclass {
    private $var; // WHY THIS LINE?

    public function sayHello() {
        $this->var = 'hello';
        echo $this->var;
    }
}
$test -> sayHello();

When I remove the line with private $var; this example works too.

Why do I have to initialize variables in classes?

Answer 1

Initializing variables has some benefits:

• You declare that you intentionally want to use the variable name. This can help highlight typos which become undeclared varible name
• You can set the scope of the variable. Do you want it to be public, protected or private? You might want it to be static
• PHP has some info about what you're doing. It may help it to optimize for faster execution.

It's good practice to declare your variables, but it isn't a requirement.