add() To throw an exception

[km3945]

$bf = new BloomFilter(1, 0.01);
$key='foo';
$bf->add($key);
for ($i=0; $i<10000; $i++) {
	var_dump($bf->has($key.$i)); // bool(true)
	$bf->add($key.$i);
	var_dump($bf->has($key.$i)); // bool(true)
}
var_dump($bf->has($key)); // bool(true)

The first parameter is the number of nodes that can be inserted or the number of memory?
If the number of memory applications, how to calculate this value?

I want to insert data, the number of nodes or memory is not enough to throw an exception, so I can do the corresponding processing.