Make ResultSets serializable.

By implementing Serializable, ResultSets can be persisted into
a persistent cache like Memcache. Unserializing needs only to set the
results again as other properties are set to their defaults.

lib/Cake/ORM/ResultSet.php

@@ -18,6 +18,7 @@
 
 use Cake\Database\Type;
 use \Iterator;
+use \Serializable;
 
 /**
  * Represents the results obtained after executing a query for an specific table
@@ -26,7 +27,7 @@
  * queries required for eager loading external associations.
  *
  */
-class ResultSet implements Iterator {
+class ResultSet implements Iterator, Serializable {
 
 /**
  * Original query from where results where generated
@@ -286,4 +287,29 @@ protected function _castValues($table, $values) {
 		return $values;
 	}
 
+/**
+ * Serialize a resultset.
+ *
+ * Part of Serializable Interface
+ *
+ * @return string Serialized object
+ */
+	public function serialize() {
+		iterator_to_array($this);
+		return serialize($this->_results);
+	}
+
+/**
+ * Unserialize a resultset.
+ *
+ * Part of Serializable Interface
+ *
+ * @param string Serialized object
+ * @return ResultSet The hydrated result set.
+ */
+	public function unserialize($serialized) {
+		$this->_results = unserialize($serialized);
+		return $this;
+	}
+
 }

lib/Cake/Test/TestCase/ORM/ResultSetTest.php

@@ -54,4 +54,44 @@ public function testRewind() {
 		$this->assertEquals($first, $second);
 	}
 
+/**
+ * An integration test for testing serialize and unserialize features.
+ *
+ * Compare the results of a query with the results iterated, with
+ * those of a different query that have been serialized/unserialized.
+ *
+ * @return void
+ */
+	public function testSerialization() {
+		$query = $this->table->find('all');
+		$results = $query->execute();
+		$expected = $results->toArray();
+
+		$query2 = $this->table->find('all');
+		$results2 = $query2->execute();
+		$serialized = serialize($results2);
+		$outcome = unserialize($serialized);
+		$this->assertEquals($expected, $outcome->toArray());
+	}
+
+/**
+ * Test iteration after serialization
+ *
+ * @return void
+ */
+	public function testIteratorAfterSerialization() {
+		$query = $this->table->find('all');
+		$results = unserialize(serialize($query->execute()));
+
+		$expected = [
+			['id' => 1, 'author_id' => 1, 'title' => 'First Article', 'body' => 'First Article Body', 'published' => 'Y'],
+			['id' => 2, 'author_id' => 3, 'title' => 'Second Article', 'body' => 'Second Article Body', 'published' => 'Y'],
+			['id' => 3, 'author_id' => 1, 'title' => 'Third Article', 'body' => 'Third Article Body', 'published' => 'Y']
+		];
+		// Use a loop to test Iterator implementation
+		foreach ($results as $i => $row) {
+			$this->assertEquals($expected[$i], $row, "Row $i does not match");
+		}
+	}
+
 }