MySql Procedure not returning value

Question

I'm unable to get the result of OUT variable in this code, am I doing wrong something? can anyone help?

BEGIN 
    DECLARE done INT DEFAULT FALSE;
    DECLARE cid INT(10);    
    DECLARE cuserid VARCHAR(50);
    DECLARE cur1 CURSOR FOR SELECT id,username FROM tblcustomer;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; 
    OPEN cur1;
    read_loop: LOOP
        FETCH cur1 INTO cid,cuserid;   
            IF done THEN
                LEAVE read_loop;
            END IF;   
            SET customers_list = CONCAT(customers_list,cid,':',cuserid,',');
    END LOOP;
    CLOSE cur1;
END

Answer 1

The procedure prototype is missing from your snippet, but assuming the below:

CREATE PROCEDURE foo(OUT customers_list VARCHAR(100))
BEGIN
    ...
    SET customers_list = 'foo-list';
END ;

This is how you would retreive your "return value":

CALL foo(@var);
SELECT @var; -- outputs "foo-list"

Strictly speaking, a procedure has no "return value". A function has:

CREATE FUNCTION bar() RETURNS VARCHAR(100)
BEGIN
    ...
    RETURN 'bar-list';
END ;

SELECT bar(); -- outputs "bar-list";