Trying to create login page using PHP and SQL -

i've been working on website login, , far, have database , register page set up, i'm trying work on login page. i've been trying retrieve data database's table. successfull @ doing on register page make sure there aren't multiple usernames of same name, copied of code , pasted onto page. problem: returns blank. please help... ._. ` khs sitespace

    <div id="header">         <a href="index.php"><img src="./images/khslogo2.png" style="margin-left:4;float:left;" width="100" hieght="100"></a>         <b>khs<span id="name">sitespace</span></a>             <!--img src="./images/menu.png" style="float:right;margin-right:6;" height="100" width="90"-->         </div>         <div id="content">             <p id="subtitle">login</p>             <div style="float:left;height:30%;">                 <form action="<?php echo $_server['php_self'];?>" method="post" id="register"><br>                     username:<br>                     <input type="text" name="name"><br><br>                     password:<br>                     <input type="password" name="pass">                     <br><br>                     <input type="submit" value="confirm">                 </form>             </div>             <div style="float:right;width:50%;border-style:none none none solid; border-color:222222;border-width:4;height:30%;">             <p style="margin-left:20;font-size:20;">output:</p>             <p style="margin-left:20;padding-bottom:15;">                 <?php                  error_reporting(0);                 @ini_set('display_errors', 0);                 session_start();                 $conn = new mysqli("localhost", "shanedrgn", "getting321", "users");                 if (!$conn) {die("failure connect");}                 $name = trim($_post['name']);                 $pass = trim($_post['pass']);                  if (empty($name) or empty($pass)) {echo "empty fields";} else {                 $name = trim($_post['name']);                 $pass = trim($_post['pass']);                      echo "check: fields arent empty...";#output                     echo "testing variables...";#output                      //error trapping                     $sql = "select username users username = '$name'";                     $data = mysqli_query($conn, $sql);                     if($record=mysqli_fetch_array($data)) {                         $nametrap = $record['username'];                     }                     $sql = "select address users address = '$address'";                     $data = mysqli_query($conn, $sql);                     if($record=mysqli_fetch_array($data)) {                         $iptrap = $record['address'];                     }                       if ($nametrap == $name) {                          echo "check: username exists...";                          if ($passtrap == $pass) {                             echo "password correct!";                             $_session['user'] = $name;                             $sql = "select * users username = '$name'";                             $data = mysqli_query($conn, $sql);                             $record=mysqli_fetch_array($data);                             session_start();                             $_session['id'] = $record['id'];                             echo "<script>alert('you have logged in!')</script>";                             sleep(4);                             header("location: ./index.php"); /* redirect browser */                             exit();                         } else { echo "password invalid";}                      } else {echo "that username doesn't exist!";echo $name.";;";echo $nametrap;}                 }                  ?>                 </p></div>                 </div>             </body>             </html>` 

edit: added missing code

you doing this:

echo "<script>alert('you have logged in!')</script>"; sleep(4); header("location: ./index.php"); /* redirect browser */ 

i understand, try, can't work. can't set header after sending body-content - using echo.

you should use javascript redirect, after 4 second timeout. use settimeout , window.location.