diff --git a/includes/model/ShiftTypes_model.php b/includes/model/ShiftTypes_model.php
index 4c71a3ed..7b502585 100644
--- a/includes/model/ShiftTypes_model.php
+++ b/includes/model/ShiftTypes_model.php
@@ -1,18 +1,66 @@
 <?php
 
+/**
+ * Delete a shift type.
+ * @param int $shifttype_id
+ */
 function ShiftType_delete($shifttype_id) {
+  return sql_query("DELETE FROM `ShiftTypes` WHERE `id`=" . sql_escape($shifttype_id));
 }
 
+/**
+ * Update a shift type.
+ *
+ * @param int $shifttype_id          
+ * @param string $name          
+ * @param int $angeltype_id          
+ * @param string $description          
+ */
 function ShiftType_update($shifttype_id, $name, $angeltype_id, $description) {
+  return sql_query("UPDATE `ShiftTypes` SET
+      `name`='" . sql_escape($name) . "', 
+      `angeltype_id`=" . sql_null($angeltype_id) . ",
+      `description`='" . sql_escape($description) . "'
+      WHERE `id`=" . sql_escape($shifttype_id));
 }
 
+/**
+ * Create a shift type.
+ *
+ * @param string $name          
+ * @param int $angeltype_id          
+ * @param string $description          
+ * @return new shifttype id
+ */
 function ShiftType_create($name, $angeltype_id, $description) {
+  $result = sql_query("INSERT INTO `ShiftTypes` SET
+      `name`='" . sql_escape($name) . "', 
+      `angeltype_id`=" . sql_null($angeltype_id) . ",
+      `description`='" . sql_escape($description) . "'");
+  if ($result === false)
+    return false;
+  return sql_id();
 }
 
+/**
+ * Get a shift type by id.
+ *
+ * @param int $shifttype_id          
+ */
 function ShiftType($shifttype_id) {
+  $shifttype = sql_select("SELECT * FROM `ShiftTypes` WHERE `id`=" . sql_escape($shifttype_id));
+  if ($shifttype === false)
+    return false;
+  if ($shifttype == null)
+    return null;
+  return $shifttype[0];
 }
 
+/**
+ * Get all shift types.
+ */
 function ShiftTypes() {
+  return sql_select("SELECT * FROM `ShiftTypes` ORDER BY `name`");
 }
 
 ?>
\ No newline at end of file