UUID v7 Generator (Time-Ordered) in Pure PHP

UUIDv4 is fully random, which means consecutive inserts scatter across a B-tree index and fragment it. UUIDv7 fixes that by putting a millisecond timestamp in the high bits, so values generated close in time sort close together, giving you the database-friendly locality of an auto-increment id while keeping global uniqueness and unguessability. This is the version you want for primary keys in 2026.

The layout is 48 bits of Unix time in milliseconds, then 4 version bits set to 7, then 12 random bits, then 2 variant bits, then 62 more random bits. The function below packs the timestamp as 12 hex characters, fills the rest from random_bytes for cryptographic quality, and masks the version nibble and the variant byte into place. No extension and no library required.

function uuidv7(): string {
    $ms = (int) (microtime(true) * 1000);
    $tsHex = str_pad(dechex($ms), 12, '0', STR_PAD_LEFT);
    $rand = random_bytes(10);
    $rand[0] = chr((ord($rand[0]) & 0x0f) | 0x70); // version 7
    $rand[2] = chr((ord($rand[2]) & 0x3f) | 0x80); // variant 10
    $hex = $tsHex . bin2hex($rand);
    return sprintf('%s-%s-%s-%s-%s',
        substr($hex, 0, 8), substr($hex, 8, 4), substr($hex, 12, 4),
        substr($hex, 16, 4), substr($hex, 20, 12));
}

$a = uuidv7();
$b = uuidv7();
echo $a . "\n" . $b . "\n";
echo "sorted in generation order: " . ($a <= $b ? 'yes' : 'no') . "\n";