PHP best way to MD5 multi-dimensional array?

Question

What is the best way to generate an MD5 (or any other hash) of a multi-dimensional array?

I could easily write a loop which would traverse through each level of the

Answer 1

Important note about serialize()

I don't recommend to use it as part of hashing function because it can return different result for the following examples. Check the example below:

Simple example:

$a = new \stdClass;
$a->test = 'sample';

$b = new \stdClass;
$b->one = $a;
$b->two = clone $a;

Produces

"O:8:"stdClass":2:{s:3:"one";O:8:"stdClass":1:{s:4:"test";s:6:"sample";}s:3:"two";O:8:"stdClass":1:{s:4:"test";s:6:"sample";}}"

But the following code:

test = 'sample';

$b = new \stdClass;
$b->one = $a;
$b->two = $a;

Output:

"O:8:"stdClass":2:{s:3:"one";O:8:"stdClass":1:{s:4:"test";s:6:"sample";}s:3:"two";r:2;}"

So instead of second object php just create link "r:2;" to the first instance. It's definitely good and correct way to serialize data, but it can lead to the issues with your hashing function.