Added DataMapper files

DataMapper/UserMapper.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace DesignPatterns;
+
+/**
+ * DataMapper pattern
+ *
+ * Purpose:
+ * A Data Mapper, is a Data Access Layer that performs bidirectional transfer of
+ * data between a persistent data store (often a relational database) and an in
+ * memory data representation (the domain layer). The goal of the pattern is to
+ * keep the in memory representation and the persistent data store independent of
+ * each other and the data mapper itself. The layer is composed of one or more
+ * mappers (or Data Access Objects), performing the data transfer. Mapper
+ * implementations vary in scope. Generic mappers will handle many different domain
+ * entity types, dedicated mappers will handle one or a few.
+ * (FROM http://en.wikipedia.org/wiki/Data_mapper_pattern)
+ *
+ * Examples:
+ * - DB Object Relational Mapper (ORM)
+ *
+ */
+class UserMapper
+{
+
+    // the table where the mapper is mapping
+    protected $_dbTable;
+
+    public function __construct(array $options = null)
+    {
+        // create new db connector on dbTable using specific table
+    }
+
+    // will save a certain user from memory to db
+    public function save(User $user)
+    {
+        $data = array(
+            'userid'   => $user->getUserId(),
+            'username' => $user->getUsername(),
+            'email'   => $user->getEmail(),
+        );
+
+        if (null === ($id = $user->getUserId())) {
+            unset($data['userid']);
+            $this->_dbTable->insert($data);
+        } else {
+            $this->_dbTable->update($data, array('userid = ?' => $id));
+        }
+    }
+
+    // will find a user from db based on the id and return it to a User object in memory
+    public function find($id, User $user)
+    {
+        $result = $this->_dbTable()->find($id);
+        if (0 == count($result)) {
+            return;
+        }
+        $row = $result->current();
+
+        $user->setOptions($row);
+    }
+
+    // will fetch all entries from a table to memory
+    public function fetchAll()
+    {
+        $resultSet = $this->_dbTable()->fetchAll();
+        $entries   = array();
+
+        foreach ($resultSet as $row) {
+            $entry = new User();
+            $entry->setOptions($row);
+            $entries[] = $entry;
+        }
+
+        return $entries;
+    }
+}