PHP form test...

Question

Test to see if a POST has occurred. If so then verify the credentials; if correct then redirect to the destination page; if incorrect then display the error message on the form page. Then output the form.

Answer 1

In its most basic form:

if (!empty($_POST))

Other ways:

// check if one of the fields are present;
if (!empty($_POST['password']))

// attach a hidden field then
<input type="hidden" name="myHidden" value="yes">
if ($_POST['myHidden'] == 'yes')

// give a name and value to the submit button, then
<input type="submit" name="subBtton" value="Send">
if ($_POST['subButton'] == 'Send')

Answer 2

Better do this in object oriënted way, I do it like this in my projects:

//check if user logged in
if(isset($_POST['sign_in'])):
    try
    {
        $userlogin = new User();
        $userlogin->loginusername = mysqli_real_escape_string($link, $_POST['username']);
        $userlogin->password = mysqli_real_escape_string($link, $_POST['password']);
        $userlogin->login();
    }
    catch(Exception $e)
    {
        header("Location: ".$siteurl."login.php?login=failed");
    }//end of catch exception
endif;//end of if user logged in

in the login() function in my user class I check if the user login is correct if not it will throw an exception (error) witch will be catched (see catch(exception...) ). I then redirect to another page but you could store the the error message in a variable like this:

$feedback = $e->getMessage();

and then just echo $feedback anywhere on your page

EDIT: this is my login function in my user class (just thought I would add it as well)

public function login()
    {
        global $link;
        $sql = mysqli_query($link, "SELECT userid, unique_id, username, password FROM user_extra WHERE username='".$this->loginusername."' AND password='".md5($this->password)."'");
        //there can only be one user with this username and password
        if(mysqli_num_rows($sql) == 1):
            $result = mysqli_fetch_object($sql);
            //sessions
            $_SESSION['userid'] = $result->userid;
            $_SESSION['username'] = $result->username;
            $_SESSION['unique_id'] = $result->unique_id;

            //cookies
            $expire=time()+60*60*24*30;
            setcookie("userid", $result->userid, $expire, "/");
            setcookie("password", $result->password, $expire, "/");
        else:
            throw new exception("Login failed");
        endif;
    }//end of function login