Hello,
I was try the script, but it's seems ulid's last 80 bits isn't unique. Here is example:
$php rr.php
01F46VF3ZZR6FYNWDYQXFA9NQT
01f46vf3zzr6fynwdyqxfa9nqv

and here is the script:

include 'Ulid/Ulid.php';
use Ulid\Ulid;

$ulid = Ulid::generate();
echo (string) $ulid, "\n"; // 01F46VF3ZZR6FYNWDYQXFA9NQT

// Or if you prefer a lowercased output
$ulid = Ulid::generate(true);
echo (string) $ulid, "\n"; // 01f46vf3zzr6fynwdyqxfa9nqv

Only the last char is different, but in specification last 80 bits need to be unique for example in Postgres ulid:

select generate_ulid() from generate_series(1, 10);

   generate_ulid        

01F46WA08EPZTRXY4108T4XAMA
01F46WA08ET4RGV447EKD337ES
01F46WA08EHWXAGBSWQMWHZVHK
01F46WA08EZTD358CC7YGKPRKX
01F46WA08EWRBMMJHCA335794Q
01F46WA08EG7H98DZY789T48VH
01F46WA08EY4X6MQW5986SAP82
01F46WA08EXY9BM9YY284C7GM2
01F46WA08E2W1CTYQ9CX1JW02N
01F46WA08EW8ESAW6QBD65ZK4A
(10 rows)

There is a fromTimestamp(.., true) which returns a lowercased string but an example in uppercase, might be a mistake?

Can we generate the timestamp from this ulid? Is there a functionality already present in this package?

Good day.
Method decodeTime() return incorrect timestamp.
In method generate(): $now = (int) (microtime(true) * 1000);.
Maybe decodeTime() must return $carry/1000 ?

See ramsey/uuid for a similar implementation.

https://github.com/ulid/spec#monotonicity

By casting to (int) at https://github.com/robinvdvleuten/php-ulid/blob/master/src/Ulid.php#L69 this is removing the float portion of the return value of microtime(true) thus checking if the current call happened within the same second (instead of millisecond) of the last request.

This should be changed such that it uses the value: microtime(true) * 1000 for milliseconds.

The $lastGenTime static property (which is supposed to be used to keep track of whether it's generating a new ULID in the same millisecond) is never updated, so the code path for handling generating a ULID in the same millisecond will never be executed (and there are no tests for this behaviour).

Is there a reason why the minimum version is set to 7.1 in composer.json? I went through the code and couldn't really find any reason for it not to be 7.0 as minimum, unless I missed something.

I'm asking because we're in the midst of finally migrating a more recent version of PHP, which we're doing in steps, but would love to start using this library from 7.0 already. I can definitely help with the changes if needed. Just curious about the why of the limitation. Thanks!

It's 2019 and, you know, there's no logical reason to support anything before php 7.1

The ulid spec does not state it explicitly, but aren't ulids supposed to be uppercase? Lowercase won't change anything when sorting and it might take less memory and database in some circumstances, but shouldn't the technique be the same over all languages?

Otherwise: Thanks for the library, good job! 👍