Register.php

<!doctype html>
<html>
<head>
<?php
   session_start();
?>

<?php
   error_reporting(E_ALL);
   ini_set("display_errors", 1);
?>
<meta charset="utf-8">
<title>Login</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<link rel="stylesheet" type="text/css" href="css/main.css" />
<link rel="stylesheet" type="text/css" href="css/creative.css" />
</head>

<body>
<h2>Test login</h2>
    <div id="form-wrapper">
    <form class="form-horizontal form-inline form-control" action="php/validation.php">
        <fieldset>

        <!-- Form Name -->
        <legend>Register</legend>

        <!-- Text input-->
        <div class="form-group">
            <label class="col-md-4 control-label" for="username">Username</label>
            <div class="col-md-4">
                <input id="username" name="username" type="text" placeholder="username" class="form-control input-md" required="">
            </div>
        </div>

        <!-- Text input-->

         <div class="form-group">
            <label class="col-md-4 control-label" for="email">Email</label>
            <div class="col-md-5">
                <input id="email" name="email" type="text" placeholder="e-mail" class="form-control input-md" required="">
            </div>
        </div>

        <!-- Appended Input-->
        <div class="form-group">
            <label class="col-md-4 control-label" for="password">Password</label>
            <div class="col-md-5">
            <div class="input-group">
                <input id="password" name="password" class="form-control" placeholder="***************" type="password" required="">
                <span class="input-group-addon">?</span>
            </div>

            </div>

        </div>
        <!-- Password input-->

         <div class="form-group">
            <label class="col-md-4 control-label" for="passwordConf">Confirm Password</label>
            <div class="col-md-5">
            <input id="passwordConf" name="passwordConf" type="password" placeholder="" class="form-control input-md" required="">
            </div>
        </div>

        <!-- Select Basic -->

         <div class="form-group">
            <label class="col-md-4 control-label" for="source">How did you hear about us?</label>
            <div class="col-md-4">
                <select id="source" name="source" class="form-control">
                <option value="Social media">Social media</option>
                <option value="Word of mouth">Word of mouth</option>
                <option value="Search engine">Search engine</option>
                <option value="Other">Other (Please specify)</option>
                </select>
            </div>
        </div>
        <div class="form-group">
            <label class="col-md-4 control-label" for="source"><a href="https://www.estiweb.co.uk/phplogin/register.php">Don't have an account?</a></label>
            <div class="col-md-4">
            <input type="submit" class="btn-primary btn btn-long" name="register" value="Register" />
            </div>
        </div>

        </fieldset>
    </form>

</div>
</body>
</html>