Mysql Stored Procedure and Php

Question

I have created this procedure:

 DROP PROCEDURE IF EXISTS add_com;
DELIMITER //
CREATE PROCEDURE add_com (cd CHAR(16), n VARCHAR(20), t VARCHAR(20), i VARCHAR(20))
BEGIN
  DECLARE num INT;
  DECLARE msg varchar(20);
set @num=select COUNT(*) from commercianti where codice_fiscale=cd;
  IF num==0 THEN
    insert into commercianti values (cd,n,i,t);
    set @msg="Commerciante inserito";
  ELSE
    insert into errors values (1);
    set @msg="Commerciante presente";
  END IF;
return @msg;
END; //

then in a PHP page I execute this code:

 <?php
$cd=$_POST['codice_fiscale'];
$n=$_POST['nominativo'];
$t=$_POST['telefono'];
$i=$_POST['indirizzo'];
if(!$cd||!$n||!$t||!$i)
echo "No data";
else{
require dirname(__FILE__) . '/' . 'dbconfig.php';
$mysqli = new MySQLI(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);
$result = $mysqli->query("CALL add_com('$cd','$n','$t','$i')");
echo $result;
}
?>

But the value of $result is undefined and seems the procedure doesn't work or isn't called.

Answer 1

If you want to get data back from a routine, you should be using a function, rather than a procedure. They have nearly the same syntax, but most notably is the RETURNS type section of the declaration. Take a look at the official documentation:

http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html

Note that the SECOND create block there is the one regarding functions. The first deals with procedures.

So I think that would look something like this:

DROP FUNCTION IF EXISTS add_com;

DELIMITER //

CREATE FUNCTION add_com (cd CHAR(16), n VARCHAR(20), t VARCHAR(20), i VARCHAR(20))
RETURNS VARCHAR(20)
BEGIN
    DECLARE num INT;
    DECLARE msg varchar(20);

    SELECT COUNT(*) INTO @num FROM commercianti WHERE codice_fiscale = cd;

    IF num==0 THEN
        insert into commercianti values (cd,n,i,t);
        set @msg="Commerciante inserito";
    ELSE
        insert into errors values (1);
        set @msg="Commerciante presente";
    END IF;
    return @msg;
END; //

I'm not 100% sure about the RETURNS VARCHAR(20) . That might have to be simply RETURNS VARCHAR .

Answer 2

Try changing

IF num==0 THEN

to

IF num=0 THEN