It makes the function remember the value of the given variable ($has_run
in your example) between multiple calls.
You could use this for different purposes, for example:
function doStuff() {
static $cache = null;
if ($cache === null) {
$cache="%heavy database stuff or something%";
}
// code using $cache
}
In this example, the if
would only be executed once. Even if multiple calls to doStuff
would occur.