Login error message in php

Question

I am new to PHP code and here I want to display an error message in login.php if the user entered incorrect userid or password.below I have written two-page code. login.php page submits the username and password to the check.php page. if username and password are correct then it redirects to the xyz.php else to the login page.

login.php //login page

<form name="login" enctype="multipart/form-data" action="checkpage.php" method="post">
            <table border="0" cellpadding="0" cellspacing="0">
            <tr>
                <th>Username</th>
                <td><input type="text" name="username" value="sandeep" onfocus="this.value=''" class="login-inp" /></td>
            </tr>
            <tr>
                <th>Password</th>
                <td><input type="password" name="password" class="login-inp" /></td>
            </tr>
            <tr>
                <th></th>
                <td valign="top"><input type="checkbox" class="checkbox-size" id="login-check" /><label for="login-check">Remember me</label></td>
            </tr>
            <tr>
                <th></th>
                <td><input type="submit" class="submit-login"  /></td>
            </tr>

            <tr><th></th><td>w want to display error message here..</td></tr>

</table></form>

checkpage.php //connection page

<?php
    session_start();
    //connecting to db
    $username=$_POST['username'];
    $pwd=$_POST['password'];
    $q="select *from xyz where username='$username' AND password='$pwd'";
    $qry=mysql_query($q);
    if(mysql_num_rows($qry)>0)
    {
        $_SESSION['username']=$username;
        echo "<script>window.open('xyz.php','_self')</script>"; 
        }
        else{

            header("location:login.php");

            }
?>

the above code work fine but i want to display the error message how could i display the error message. please guide me.

Answer 1

You can set the message to session in your check.php script and then unset immediately after getting it for display (AKA "read once"):

$_SESSION['message'] = 'Your message';

and then (in login.php, where you want the message to be displayed):

if (isset($_SESSION['message']))
{
    echo $_SESSION['message'];
    unset($_SESSION['message']);
}

Answer 2

Give a space between * and from in query.

$q="select * from xyz where username='$username' AND password='$pwd'";

1. For error message you can set a flag like error= 1

   header("location:login.php?error=1"); and in login.php you can check this flag and display a message like

     <?php   If(isset($_GET['error']) && $_GET['error'] == 1){ ?>
           <h3>Invalid username or password</h3>    
     <?php } ?>
   

2. You can set a session of error and display it in login.php and unset it after displaying.

   but donot forget to use session_start in both pages session_start(); //on top of page

   before header code add $_SESSION['error'] = "you message here"

in login.php

          <?php if(isset($_SESSION['error'])) {
                echo $_SESSION['error'];
           }

          ?>