sqli4.php

<?php
include 'vulnconf.php';
if(isset($_POST['submit'])) {
	$username = $_POST['username']; 
	$password = $_POST['password'];
	$sql = "INSERT INTO users (`id`, `username`, `password`) VALUES ('','$username','$password')";
	$result=mysqli_query($link,$sql);
	if($result==true){
		$ok="<div class='alert alert-success' role='alert'>The operation was completed successfully<</div>";
	}else {
		$ok="<div class='alert alert-danger' role='alert'>Error</div>";
	}



}
 include 'ust.php'; 
?>
<?php  echo (!empty($ok) ? $ok : ""); ?>   
<div id="page-content-wrapper">
	<!-- 2 -->
	<div class="container-fluid">
		<!-- 3 -->
		<div class="row">
			<!-- 4 -->	
			<div class="col-lg-6">
            <h1>Sql Injection 104</h1>

<div class="well">
<form action="sqli4.php" method="POST">

  <div class="form-group">
    <label for="exampleInputEmail1">Username</label>
    <input name="username" class="form-control" id="exampleInputEmail1" placeholder="">
  </div>

  <div class="form-group">
    <label for="exampleInputPassword1">Password</label>
    <input type="password" name="password" class="form-control" id="exampleInputPassword1" placeholder="">
  </div>

  <button type="submit" name="submit" class="btn btn-default">Submit</button>
</form>
</div>
<br>
<a href="sqli5.php">Click to move to the next stage</a>

				<!-- /4 -->
				</div>
			<!-- /3 -->
			</div>
		<!-- /2 -->
		</div>
<?php include 'alt.php'; ?>