How to determine the occurrence of one subnet in another? (algorithm in PHP)?

Question

Algorithms

Hello, there are 2 subnets with masks, let's say

$subnet1 = '10.5.1.0/20';
$subnet2 = '10.5.1.0/24';

How to check that one subnet is part of another?
I found such a solution - get all the addresses of each subnet, take the first and last, convert to integers (ip2long) and stupidly check the occurrence of one range in another.
But something tells me that there is a more beautiful solution - for example, somehow make it XOR, but I don’t understand how to do it right.
Can you tell me?

Answer 1

Take a network with a smaller mask (/24),
convert its IP (first) to long,
check if this IP enters a network with a wider mask (/20).
PS Network 10.5.1.0/20 is not possible because its lower 12 bits must be zeros.