namespaces - What does a (backslash) do in PHP (5.3+)?

Question

What does a do in PHP?

For example, CSRF4PHP has FALSE, session_id, and Exception:

public function __construct($timeout=300, $acceptGet=FALSE){
    $this->timeout = $timeout;
    if (session_id()) {
        $this->acceptGet = (bool) $acceptGet;
    } else {
        throw new Exception('Could not find session id', 1);
    }
}

Answer 1

(backslash) is the namespace separator in PHP 5.3.

A before the beginning of a function represents the Global Namespace.

Putting it there will ensure that the function called is from the global namespace, even if there is a function by the same name in the current namespace.