Improve PHP performance by caching database results (2)_PHP tutorial

Create Notification Handler
Now you can create a notification handler that will send change notifications to clients with the help of the sendNotification
procedure described above. Let's take a look at the PL/SQL procedure orders_nf_callback in Listing 2.
Listing 2.
Notification handler that handles notifications of changes to the OE.ORDERS table

CREATE OR REPLACE PROCEDURE orders_nf_callback (ntfnds IN SYS.CHNF$_DESC) IS <br>tblname VARCHAR2(60); <br>numtables NUMBER; <br>event_type NUMBER; <br>row_id VARCHAR2(20); <br>numrows NUMBER; <br>ord_id VARCHAR2(12); <br>url VARCHAR2(256) := 'http://webserverhost/phpcache/dropResults.php?order_no='; <br>BEGIN <br>event_type := ntfnds.event_type; <br>numtables := ntfnds.numtables; <br>IF (event_type = DBMS_CHANGE_NOTIFICATION.EVENT_OBJCHANGE) THEN <br>FOR i IN 1..numtables LOOP <br>tblname := ntfnds.table_desc_array(i).table_name; <br>IF (bitand(ntfnds.table_desc_array(i).opflags,  <br>DBMS_CHANGE_NOTIFICATION.ALL_ROWS) = 0) THEN <br>numrows := ntfnds.table_desc_array(i).numrows; <br>ELSE <br>numrows :=0; <br>END IF; <br>IF (tblname = 'OE.ORDERS') THEN <br>FOR j IN 1..numrows LOOP <br>row_id := ntfnds.table_desc_array(i).row_desc_array(j).row_id; <br>SELECT order_id INTO ord_id FROM orders WHERE rowid = row_id; <br>sendNotification(url, tblname, ord_id);  <br>END LOOP; <br>END IF; <br>END LOOP; <br>END IF; <br>COMMIT; <br>END; <br>/ <br>

As shown in "Listing 2", this notification handler will SYS The .CHNF$_DESC
object is used as a parameter, and its properties are then used to get the details of that change. In this example, this notification handler will only handle database in response to DML or DDL
changes made to registered objects (that is, only if the notification type is EVENT_OBJCHANGE
) and ignore notifications about other database events such as instance startup or instance shutdown. Starting with the above version, handlers can handle change notifications issued for each affected row in the OE.ORDERS
table. Later in this article, in the "Add a table to an existing registration" section, you will add a few lines of code to the handler so that it can handle notifications for modified rows in the OE.ORDER_ITEMS
table.

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