ICursor: improved PHPDoc

src/PostgresDriver/ICursor.php

@@ -3,10 +3,23 @@
  * This file is part of mappi/store.
  */
 namespace Grifart\Mappi\Store\PostgresDriver;
-use Dibi\Connection;
 
 /**
  * Represents PostgreSQL cursor
+ *
+ * Cursor works same as tape. When you have 3 items on it it has these indexes.
+ * index:     0  1  2  3  4
+ * value:     -  1  2  3  -
+ * head:      ^
+ *
+ * - You have HEAD which you can move around and read records before, after or current.
+ * - You cannot ask for current position.
+ * - You can move to absolute position from left or from right
+ * - You can more relatively to any side
+ * - BEGINNING (0) and END (4) has no value
+ * - Cursor starts at BEGINNING
+ * - When you move too far you end in one of ends
+ * 
  * @link http://www.postgresql.org/docs/9.5/static/plpgsql-cursors.html
  * @link http://www.postgresql.org/docs/8.1/static/sql-fetch.html
  * @link http://www.postgresql.org/docs/8.1/static/sql-move.html