register including post fail

Question

I am trying to build a login system with registration etc. now for the registration i use a form and the method "post". Now it fails in what i think is sending the input trough the post. can you help me fix it? here is the code involved in it:

above !doctype

<?php
include('connect.php');
// If the values are posted, insert them into the database.
if (isset($_POST["username"]) && isset($_POST["password"])){
    $username = $_POST["username"];
    $email = $_POST["email"];
    $password = $_POST["password"];

    $query = "INSERT INTO `user` (username, password, email) VALUES ($username, $password, $email)";
    $result = mysqli_query($query);
    if($result){
        $msg = "User Created Successfully.";
    }
else
  {echo "fail";}
}
?>

the form:

<div class="register-form">
<?php
if(isset($msg) & !empty($msg)){
    echo $msg;
}
?>
<h1>Registreer</h1>
<form action="" method="POST">
<p><label>User Name : </label>
<input id="username" type="text" name="username" placeholder="username" /></p>

<p><label>E-Mail&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; : </label>
 <input id="password" type="email" name="email" required placeholder="name@email.com" /></p>

 <p><label>Password&nbsp;&nbsp; : </label>
 <input id="password" type="password" name="password" placeholder="password" /></p>

<a class="btn" href="login.php">Login</a>
<input class="btn register" type="submit" name="submit" value="Registreer" />
</form>

</div>    

The connect.php

<?php
$servername = "localhost";
$username = "sqluser";
$password = "Welkom01!";
$dbname = "users";

$connection = mysqli_connect($servername, $username, $password);
if (!$connection){
die("Database Connection Failed". mysqli_error($connection));
}
$select_db = mysqli_select_db($connection, $dbname);
if (!$select_db){
die("Database Selection Failed" . mysqli_error($connection));
}
?>

Thanks in advance.

Answer 1

As per your originally posted question and without marking it as an edit under your newly edited question, should anyone wonder why the answer.

---

Since we're more than likely dealing with strings

VALUES ($username, $password, $email)

needs to be wrapped inside quotes:

VALUES ('$username', '$password', '$email')

you also need to pass DB connection to your query $result = mysqli_query($query);

Edit: (you added your DB connection code after) from your original post

Since you've not shown what your DB connection is, this would be something like

$result = mysqli_query($connection,$query);

plus, adding or die(mysqli_error($connection)) to mysqli_query()

You also have a missing & in if(isset($msg) & !empty($msg)){ which should read as if(isset($msg) && !empty($msg)){

---

• However, your present code is open to SQL injection.
  Use prepared statements, or PDO with prepared statements, they're much safer.

---

Passwords

I also noticed that you may be storing passwords in plain text. This is not recommended.

Use one of the following:

• CRYPT_BLOWFISH
• crypt()
• bcrypt()
• scrypt()
• On OPENWALL
• PBKDF2
• PBKDF2 on PHP.net
• PHP 5.5's password_hash() function.
• Compatibility pack (if PHP < 5.5) https://github.com/ircmaxell/password_compat/

Other links:

• PBKDF2 For PHP