updated php doc

framework/yii/db/DataReader.php

@@ -40,7 +40,7 @@ use yii\base\InvalidCallException;
  * for more details about possible fetch mode.
  *
  * @property integer $columnCount The number of columns in the result set. This property is read-only.
- * @property mixed $fetchMode Fetch mode. This property is write-only.
+ * @property integer $fetchMode Fetch mode. This property is write-only.
  * @property boolean $isClosed Whether the reader is closed or not. This property is read-only.
  * @property integer $rowCount Number of rows contained in the result. This property is read-only.
  *