Strict Standards: Only variables should be passed by reference in m_auth

Question

I am working on a login system for a project using MVC programming and ran into this error. Here is the code, the problem line is #31

This login system is a tutoria

Answer 1

Add parenthesis:

$stmt->bind_param("ss", $user, (md5($pass . $this->salt)));

Answer 2

bind_param's params are references to variables. You can't use md5() there. You need to save it to a variable first.

$userPass = md5($pass . $this->salt);
$stmt->bind_param("ss", $user, $userPass);

Answer 3

The problem is that the 3rd parameter is the result of a function call:

md5($pass . $this->salt)

You need to save that value to a variable before passing it to bind_param so that it can be passed by reference.

Example:

$password = md5($pass . $this->salt);  
$stmt->bind_param("ss", $user, $password);

Also, don't use md5 to hash passwords.

Answer 4

This was likely fixed in PHP 5.4 as part of Function Array Dereferencing (FAD) (revision 300266).

Alternatively as workaround try adding extra brackets, e.g.

$stmt->bind_param("ss", $user, (md5($pass . $this->salt)));

which would dereference the method/function return, see: (<5.6) Occasionally significant parentheses.