Supporting Features Added in MySQL 5 - Mastering phpMyAdmin 3.4 for Effective MySQL Management - page 291

Entering the procedure
We then enter the procedure's code in the main query box:
CREATE PROCEDURE `add_page`(IN param_isbn VARCHAR(25),
IN param_pages INT, OUT param_message VARCHAR(100))
BEGIN
IF param_pages > 100 THEN
SET param_message = 'the number of pages is too big';
ELSE
UPDATE book SET page_count = page_count + param_pages WHERE
isbn=param_isbn;
SET param_message = 'success';
END IF;
END
//
On clicking Go , we get a success message if the syntax is correct. If it is not, well it's
time to revise our typing abilities or debug our syntax. Unfortunately, MySQL does
not come with a procedure debugger.
Testing the procedure
Again, in the query box, we test our procedure by entering the following statements.
Here, we are using a SQL variable, @message , which will receive the contents of the
OUT parameter param_message :
call add_page('1-234567-22-0', 4, @message);
SELECT @message;
If all went well, we should see that the @message variable contains success .
We can then verify whether the page count for this topic has increased. We also need
to test the problematic case:
call add_page('1-234567-22-0', 101, @message);
SELECT @message;
This procedure is now available for calling (for example) from your PHP scripts
using the mysqli extension, which is the one recommended to access all the
functionalities provided by MySQL 4.1 and above.