How can I safely generate deterministic cache keys for complex PHP arrays (including objects) without risking collisions?

I'm building a caching layer in a PHP application where cache keys must be generated from input parameters. The parameters can be nested arrays or objects, and I need a deterministic cache key that uniquely represents the data.

For example, these two arrays should produce the same cache key:

$a = [ "user" => 10, "filters" => ["active" => true, "role" => "admin"] ]; $b = [ "filters" => ["role" => "admin", "active" => true], "user" => 10 ];

The order of associative keys should not affect the cache key.

My first idea was something like this:

$key = md5(json_encode($data));

But this fails because:

Associative array order changes the JSON string.

Objects may contain private/protected properties.

Floating point precision may cause inconsistencies.

json_encode might serialize values differently depending on encoding flags.

Another approach I tried was recursively sorting the array before hashing:

function normalize($data) { if (is_array($data)) { ksort($data); foreach ($data as &$v) { $v = normalize($v); } } return $data; } $key = md5(json_encode(normalize($data)));

This works for arrays, but becomes messy when:

objects are included

objects implement JsonSerializable

objects contain circular references

My requirements:

deterministic result for same logical data

associative array order ignored

works with arrays + objects

avoids collisions as much as possible

reasonably fast (used in caching layer)

What would be the best practice in PHP to generate a stable hash/key for complex data structures?

Is there a known approach or library for this problem?