Fix UUIDv6 getTime() near Unix Epoch (#36)

* Fix UUIDv6 `getTime()` near Unix Epoch

Author: oittaa

src/UUID.php

@@ -260,7 +260,8 @@ public static function getTime(string $uuid): ?string
         $timehex = '0' . substr($uuid, 0, 12) . substr($uuid, 13, 3);
         $retval = null;
         if ($version === 6) {
-            $retval = substr_replace(strval(hexdec($timehex) - self::TIME_OFFSET_INT), '.', -7, 0);
+            $retval = strval(hexdec($timehex) - self::TIME_OFFSET_INT);
+            $retval = substr_replace(str_pad($retval, 8, '0', \STR_PAD_LEFT), '.', -7, 0);
         } elseif ($version === 7) {
             $unixts = hexdec(substr($timehex, 0, 10));
             $subsec = str_pad(strval(self::decodeSubsec(hexdec(substr($timehex, 10)))), 7, '0', \STR_PAD_LEFT);

tests/UuidTest.php

@@ -212,4 +212,10 @@ public function testGetTimeNull()
         $uuid4_time = UUID::getTime(UUID::uuid4());
         $this->assertNull($uuid4_time);
     }
+
+    public function testGetTimeNearEpoch()
+    {
+        $uuid6_time = UUID::getTime('1b21dd21-3814-6001-76fa-54fb559c5fcd');
+        $this->assertSame($uuid6_time, '0.0000001');
+    }
 }