Add missing null type in CActiveRecord PHPDoc (#4202)

framework/db/ar/CActiveRecord.php

@@ -1455,7 +1455,7 @@ public function setTableAlias($alias)
 	 * @param array $params parameters to be bound to an SQL statement.
 	 * This is only used when the first parameter is a string (query condition).
 	 * In other cases, please use {@link CDbCriteria::params} to set parameters.
-	 * @return static the record found. Null if no record is found.
+	 * @return static|null the record found. Null if no record is found.
 	 */
 	public function find($condition='',$params=array())
 	{
@@ -1484,7 +1484,7 @@ public function findAll($condition='',$params=array())
 	 * @param mixed $pk primary key value(s). Use array for multiple primary keys. For composite key, each key value must be an array (column name=>column value).
 	 * @param mixed $condition query condition or criteria.
 	 * @param array $params parameters to be bound to an SQL statement.
-	 * @return static the record found. Null if none is found.
+	 * @return static|null the record found. Null if none is found.
 	 */
 	public function findByPk($pk,$condition='',$params=array())
 	{
@@ -1517,7 +1517,7 @@ public function findAllByPk($pk,$condition='',$params=array())
 	 * An attribute value can be an array which will be used to generate an IN condition.
 	 * @param mixed $condition query condition or criteria.
 	 * @param array $params parameters to be bound to an SQL statement.
-	 * @return static the record found. Null if none is found.
+	 * @return static|null the record found. Null if none is found.
 	 */
 	public function findByAttributes($attributes,$condition='',$params=array())
 	{
@@ -1548,7 +1548,7 @@ public function findAllByAttributes($attributes,$condition='',$params=array())
 	 * Finds a single active record with the specified SQL statement.
 	 * @param string $sql the SQL statement
 	 * @param array $params parameters to be bound to the SQL statement
-	 * @return static the record found. Null if none is found.
+	 * @return static|null the record found. Null if none is found.
 	 */
 	public function findBySql($sql,$params=array())
 	{
@@ -1850,7 +1850,7 @@ public function deleteAllByAttributes($attributes,$condition='',$params=array())
 	 * This method is internally used by the find methods.
 	 * @param array $attributes attribute values (column name=>column value)
 	 * @param boolean $callAfterFind whether to call {@link afterFind} after the record is populated.
-	 * @return static the newly created active record. The class of the object is the same as the model class.
+	 * @return static|null the newly created active record. The class of the object is the same as the model class.
 	 * Null is returned if the input data is false.
 	 */
 	public function populateRecord($attributes,$callAfterFind=true)