Hi. I have a problem here.
When I write a username that doesn't exist I get no message up on the page.

PHP Code:

---

<?php

$username = $_POST['username'];
$password = $_POST['password'];

if ($username&&$password) 
    {
        $connect = mysql_connect("mysql.<MASKED>.com","<MASKED>","<MASKED>")or die(mysql_error());
        mysql_select_db("u875234194_login")or die(mysql_error());
        $query = mysql_query("SELECT * FROM members WHERE username='$username'");
    
        $numrows = mysql_num_rows($query)or die(mysql_error());
        
        if ($numrows!=0)
            {
                while ($row = mysql_fetch_assoc($query))
                    {
                        $dbusername = $row['username'];
                        $dbpassword = $row['password'];
                    }
                    
                    if ($username==$dbusername&&$password==$dbpassword)
                        {
                            echo "You're logged in";
                        }
                    else
                        {
                            echo "Wrong password";
                        }
            }
        else
            {
                die("That user doesnt exist");
            }
    }
else
    {
                ?>
                    <script type='text/javascript'>
                        alert("Please enter user and password");
                        history.go(-1);
                    </script>
                <?php
    }
                ?>

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If I change

PHP Code:

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if (numrows!=0) 


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to

PHP Code:

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if (numrows==0) 


---

and write a username that does exist, I do get my That user doesn't exist message

PHP Code:

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else { die("That user doesn't exist") 


---

Change the while loop to this:

Code:

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while ($row = mysql_fetch_assoc($query))
          {
                        $dbusername = $row['username'];
                        $dbpassword = $row['password'];
             
                   
                    if ($username==$dbusername&&$password==$dbpassword)
                        {
                            echo "You're logged in";
                            break;
                        }
                    elseif ($username==$dbusername&&$password !=$dbpassword)
                        {
                            echo "Wrong password";
                            break; 
                        }
                }

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The problem is that you are loading the dbusername/dbpassword with an empty row since you are checking after the while loop is over.