PHP: Why mysqli_fetch_assoc() won't work? I am using mysqli_stmt_get_result()

Question

I have a MySQL query that was working up until I changed it in order to use prepared statements. I cannot figure out why I do get this error:

mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, object given

The query (of this log in form) should return just one result:

    $conectar = mysqli_connect(localhost, USER, PASS, DATABASE);

    //from the log in form
    $email = $_POST['email'];
    $clave = $_POST['clave']; 

//this should get me just one result: the user to which the email belongs.
    $consulta = "SELECT usuarios.userID, usuarios.userPass, usuarios.userEmail, usuarios.userPass, usuarios.userFechaGeneracion, usuarios.userNombres, rolesUsuarios.nombreRol,
                 GROUP_CONCAT(rolesUsuarios.nombreRol SEPARATOR '|') AS roles
                 FROM rolesUsuarios, usuarios 
                 WHERE usuarios.userEmail=?
                 AND rolesUsuarios.userID = usuarios.userID
                 GROUP BY usuarios.userID
                 ";
    $buscarUsuario = mysqli_prepare($conectar,$consulta);
    mysqli_stmt_bind_param($buscarUsuario, 's', $email);
    mysqli_stmt_execute($buscarUsuario);

        if (mysqli_stmt_get_result($buscarUsuario)) { 
            $row = mysqli_fetch_assoc($buscarUsuario);
            $originalPass = $row['userPass'];
...

Why isn't working? The query in itself should return an array with that result, containing the User Name Email, the Password (a hashed value, actually), his Role, etc...

Answer 1

You are close:

    //  vvvvvvv--- this is missing
    if ($result = mysqli_stmt_get_result($buscarUsuario)) { 
        $row = mysqli_fetch_assoc($result);
        //                        ^^^^^^^--- & needs to be used here

The reason is that $buscarUsuario is a statement "handle", not an actual result set from the database. You use that "handle" to get the actual result set. Following the trail of logic using the documentation:

mysqli_stmt_get_result takes a mysqli_stmt argument and returns a mysqli_result :

mysqli_result mysqli_stmt_get_result ( mysqli_stmt $stmt )

mysqli_fetch_assoc takes a mysqli_result :

array mysqli_fetch_assoc ( mysqli_result $result )

Answer 2

According to the documentation ( https://secure.php.net/manual/en/mysqli-stmt.get-result.php ), this is how you use mysqli's prepared statements, where $stmt is $buscarUsuario in your code snippet:

mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);
$row = mysqli_fetch_array($result, MYSQLI_NUM);

Answer 3

When using mysqli_stmt_execute(), the mysqli_stmt_fetch() function must be used to fetch the data prior to performing any additional queries. Official Doc

while (mysqli_stmt_fetch($stmt)) {

}