Question

I’m trying to improve my coding ninja h4x skills, and I’m currently looking at different frameworks, and I have found sample code that’s pretty hard to google.

I am looking at the FUEL framework used in a project.

The sample I don’t understand is

$data and $this->template->set_global($data);

What is the and keyword doing in this line of code? It is used many places in the framework and it’s the first that I have found that uses it.

Answer 1

This is a type of “short circuit evaluation“. The and/&& implies that both sides of the comparison must evaluate to TRUE.

The item on the left of the and/&& is evaluated to TRUE/FALSE and if TRUE, the item on the right is executed and evaluated. If the left item is FALSE, execution halts and the right side isn’t evaluated.

$data = FALSE;
// $this->template->set_global($data) doesn't get evaluated!
$data and $this->template->set_global($data);

$data = TRUE;
// $this->template->set_global($data) gets evaluated
$data and $this->template->set_global($data);

Note these don’t have to be actual boolean TRUE/FALSE, but can also be truthy/falsy values according to PHP’s evaluation rules. See the PHP boolean docs for more info on evaluation rules.