callback function return return($var & 1)?

Question

I have read the PHP Manuel about array_filter

Answer 1

& is bitwise "and" operator. With 1, 3, 5 (and other odd numbers) $var & 1 will result in "1", with 0, 2, 4 (and other even numbers) - in "0".

Answer 2

it returns 0 or 1, depending on your $var

if $var is odd number, ex. (1, 3, 5 ...) it $var & 1 returns 1, otherwise (2, 4, 6) $var & 1 returns 0