registration form can't connect in phpmyadmin db - php

Question

I have a registration form and I want it to connect to my database. I used phpmyadmin as my database. The code that I used to connect the two is below:
db.php
<?php
$hostname = "127.0.0.1";
$user = 'root';
$password = '';
$db = 'dbTest';
//connection to db
$conn = mysqli_connect("$hostname", "$user", "$password", "$db")or die(mysqli_error());
mysqli_select_db($conn, "peanat")or die(mysqli_error());
$username = $_POST['username'];
$password = $_POST['password'];
$username = strtolower(trim($_POST["username"]));
$username = filter_var($username, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW|FILTER_FLAG_STRIP_HIGH);
$checkUsername = mysqli_query($conn, "Select username * FROM users WHERE Username='$username'");
$numrows = mysqli_num_rows($checkUsername);
if($numrows!==1) {
echo "Username not available";
}else{
$sql = "INSERT INTO `users` (`Username`, `Password`) VALUES ('$username', '$password')";
if(!mysqli_query($conn, $sql)) {
die(mysqli_error());
} else {
echo "1 record added";
}
}
?>
this is my reg form
<form id="register" action="db.php" method="post" >
<div class="col-4">
<label>
Username
<input placeholder="" id="username" name="username">
</label>
</div>
<div class="col-4">
<label>Password
<input type="password" placeholder="" id="password" name="password">
</label>
</div>
<div class="col-4">
<label>Confirm Password
<input type="password" placeholder="" id="password2" name="password2">
</label>
</div>
<div class="col-submit">
<input type="submit" class="submitbtn" name="register" value="Register">
</div>
</form>
now the problem I'm encountering is, every time I click the register button, it just goes to the designated page and it shows the code of that page. where do you think is my error...

Answer 1

Place the two files (db.php & reg.HTML) into your local web server folder. (eg. C:/xampp/htdocs/form/
Open any internet browser and type in the path to your HTML file. Eg. Local host/form/reg.html and hit enter.
You should get HTML form displayed on the browser and you're done.