The value of the output is always null. PHP and MySql

I have a problem. The procedure returns an output value (Boolean type) and when I pick it up in the php code it is always null. Any solution??

Thank you!

MYSQL STORED PROCEDURE:

BEGIN
   IF EXISTS (SELECT * FROM client WHERE user LIKE p_user AND
         password LIKE p_contrasena) THEN
        SET p_out = 1;
ELSE
        SET p_out = 0;
  END IF;
END

PHP CODE:

connect_error) {
die ("Connection failed:". $ connection-> connect_error);}

// Create connection with the database
$ db = mysqli_select_db ($ connection, $ database);

// Declare the input variables
$ user = $ _ POST['txtUsuario'];
$ contrasena = $ _ POST['txtContrasena'];


$ sqlpro = "CALL pr_login ($ user, $ password, '@ p_output')";
$ rdo = mysqli_query ($ connection, "SELECT @p_salida as output");
echo $ rdo;
      $ row = mysqli_fetch_assoc ($ rdo);
      if ($ row['salida']== 1)
           echo 'GOOD';
      else
        I miss 'BAD';

 }
 else
 ?>
 
 

User:
Password:
`