I coded in php for a login test but the data is not showing in the database : <p>I have attempted to make a login test using php but the data is not showing inside the database..What's the problem?Following are the lines of code for signup.</p>

<p>` 

<pre><code> include 'databasehandler.php';

  $first=$_POST['first'];
  $last=$_POST['last'];
 $uid=$_POST['uid'];
 $password=$_POST['password'];



    $sql="INSERT INTO profile(first, last, uid, password)  
   VALUES('$first, $last, $uid, $password')";


     $result=mysqli_query($conn,$sql);



        header("Location:main.php");`
</code></pre>
