title: PHP is inserting two duplicate rows in MYSQL database
body: <p>I am having trouble with PHP and MYSQL. I have an HTML form which when submitted runs the following PHP script.The problem is that the following PHP code is inserting the data into the database twice. I think it is something to do with the following PHP and not the database:</p>
  
  <pre><code>&lt;?php
  
  $first_name = $_POST['firstname'];
  $last_name = $_POST['lastname'];
  $display_name = $_POST['displayname'];
  $email = $_POST['email'];
  $password = $_POST['password'];
  $add_line1 = $_POST['addline1'];
  $add_line2 = $_POST['addline2'];
  $city = $_POST['city'];
  $county = $_POST['county'];
  $postcode = $_POST['postcode'];
  
  $sql = "INSERT INTO members (memberID, 
  memberPassword, 
  memberFirstName, 
  memberLastName,
  memberAddressLine1, 
  memberAddressLine2, 
  memberCity,
  memberCounty, 
  memberPostcode, 
  memberDisplayName) 
  VALUES ('$email', 
  '$password', '$first_name', '$last_name',
   '$add_line1', '$add_line2','$city',
   '$county', '$postcode', '$display_name')";
  
  if (!mysqli_query($conn,$sql))
  {
       die('Error: ' . mysqli_error($conn));
  }
  mysqli_query($conn,$sql);
  echo 'Guest Added';
  mysqli_close($conn);
  
  ?&gt;
  </code></pre>