Question

I’m planning on developing a CMS using PHP and MySQL that utilises MySQL stored procedures to perform prepared statement queries to my MySQL database. It’s been a long time since I developed in PHP (back in the procedural days) so I’m going to try and implement this system using the new OOP structure of PHP. Before I do that, I need to get to grips with the simple issue of returning the output parameter of my MySQL stored procedure to a simple php page. This is simply a test so that I can get the syntax correct before developing my first php class so the initial code posted here is procedural.

First, there is my stored procedure:

    DELIMITER $$
    DROP PROCEDURE IF EXISTS `text_development`.`get_user`$$
    CREATE PROCEDURE  `text_development`.`get_user`
    (
    IN userId INT,
    OUT user_name VARCHAR(100)
    )
    BEGIN
    SELECT username
    INTO user_name
    FROM user
    WHERE user_id = userId;
    END $$
    DELIMITER ;

Then there is my two php files:

    <?php
    //db_config.php
    $mysqli_host = "localhost";
    $mysqli_user = "root"; //I'm not stupid enough to use this in development
    $mysqli_pass = "root"; //before anyone comments about the root usage
    $mysqli_db = "text_development";
    ?>


    <?php
    //index.php
    require('incl/db_config.php');
    $dbConnection = new Mysqli($mysqli_host, $mysqli_user, $mysqli_pass, $mysqli_db) or die(mysql_error());
    print '<h1>Stored Procedure Retrieval Test</h1>';
    $id = 1;
    $return = '';
    $result = $dbConnection->query( 'CALL get_user($id,$return)');
    print $result;
    ?>

My problem arises with the index.php page. It doesn’t actually seem to return anything. When executing the stored procedure in PHPMyAdmin the username test is returned when I pass in the user id of 1 however nothing is returned to the screen when calling the function in php. I’ve also tried printing $return as well but this just returns an empty string (as I define in the code above). I’ve tried using this online tutorial but the solutions there do not seem to work :

http://www.joeyrivera.com/2009/using-mysql-stored-procedures-with-php-mysqlmysqlipdo/

Does anyone know what I’m doing wrong here and why the return parameter of this stored procedure is not being printed to the screen?

Answer 1

Firstly, you refer to a tutorial on PDO, but you use Mysqli.

Second: convert:

$result = $dbConnection->query( 'CALL get_user($id,$return)');

to (notice the double quotes, and the @return`):

$result = $dbConnection->query( "CALL get_user({$id},@return)");

and then, later, do:

$result = $dbConnection->query( 'SELECT @return');

If the SP is a SELECT, then you do it they you wrote it.

Reason is, the SP does not return to PHP anything, it returns the value into the MySQL variable (@return)(scop is in MySQL), so you need to query this variable in a separate call. If it was a call to a simple select SP, then it would return values as any other select statement.