What is the function of & like in context of why 4 & 3 in php is 0 like how is it works

Answer 1

Example:
Input: $First = 5, $Second = 3
Output: The bitwise & of both these value will be 1.
Explanation:
Binary representation of 5 is 0101 and 3 is 0011.
Therefore their bitwise & will be 0001 (i.e. set
if both first and second have their bit set.)

Now you can try with 4 & 3