Fixes #91: Made Uuid's serializable.

src/Uuid.php

@@ -187,6 +187,32 @@ class Uuid implements UuidInterface
         return $this->toString();
     }
 
+    /**
+     * Converts this UUID object to a string when the object is serialized
+     * with `serialize()`
+     *
+     * @return string
+     * @link http://php.net/manual/en/class.serializable.php
+     */
+    public function serialize()
+    {
+        return $this->toString();
+    }
+
+    /**
+     * Re-constructs the object from its serialized form.
+     *
+     * @param string $serialized
+     * @link http://php.net/manual/en/class.serializable.php
+     */
+    public function unserialize($serialized)
+    {
+        $uuid = self::fromString($serialized);
+        $this->codec = $uuid->codec;
+        $this->converter = $uuid->converter;
+        $this->fields = $uuid->fields;
+    }
+
     public function compareTo(UuidInterface $other)
     {
         $comparison = 0;

src/UuidInterface.php

@@ -21,7 +21,7 @@ use Ramsey\Uuid\Exception\UnsupportedOperationException;
  * UuidInterface defines common functionality for all universally unique
  * identifiers (UUIDs)
  */
-interface UuidInterface extends \JsonSerializable
+interface UuidInterface extends \JsonSerializable, \Serializable
 {
     /**
      * Compares this UUID to the specified UUID.

tests/src/UuidTest.php

@@ -1840,4 +1840,12 @@ class UuidTest extends TestCase
 
         $this->assertEquals('"' . $uuid->toString() . '"', json_encode($uuid));
     }
+
+    public function testSerialize()
+    {
+        $uuid = Uuid::uuid4();
+        $serialized = serialize($uuid);
+        $unserializedUuid = unserialize($serialized);
+        $this->assertTrue($uuid->equals($unserializedUuid));
+    }
 }