PHP convert ULID string to integer

examples.php

<?php

/*
PHP helper to convert ULID strings to 64-bit integers.
    - Minimal collisions
    - Deterministic
    - Fast and Native
*/

// Let's say we want to determine the correct shard for the record with ULID

$ulid = '01KE43A66G7XBNBZWHSD06DJVX';

$ulidInt = ulidToInt($ulid);

$totalShards = 5;

$shardIndex = $ulidInt % $totalShards;

function.php

<?php

/**
 * Convert a ULID to a 64-bit integer.
 *
 * @param string $ulid The ULID string to convert.
 * @param int|null $substringPart Optional hex length (1-16) to truncate hash before conversion.
 * @return int A 64-bit integer derived from the ULID using FNV-1a hashing.
 * @throws RuntimeException If the fnv1a64 hashing algorithm is unavailable.
 * @throws InvalidArgumentException If the ULID format or substringPart is invalid.
 */
function ulidToInt(string $ulid, ?int $substringPart = null): int
{
    static $hashingAlgorithm = null;
    if ($hashingAlgorithm === null) {
        $hashingAlgorithm = in_array('fnv1a64', hash_algos(), true);
    }
    if (!$hashingAlgorithm) {
        throw new RuntimeException('The "fnv1a64" hashing algorithm is not available.');
    }
    $ulid = strtoupper($ulid);
    if (strlen($ulid) !== 26 || !preg_match('/^[0-7][0-9A-HJKMNP-TV-Z]{25}$/', $ulid)) {
        throw new InvalidArgumentException('Invalid ULID format.');
    }
    if ($substringPart !== null && ($substringPart < 1 || $substringPart > 16)) {
        throw new InvalidArgumentException('substringPart must be between 1 and 16.');
    }
    $hash = hash('fnv1a64', $ulid);
    if ($substringPart !== null) {
        $hash = substr($hash, 0, $substringPart);
    }
    return hexdec($hash);
}