include_once 'includes/dbh.php';

$username = $conn->real_escape_string($_POST['username']);  <br/>
$password = $conn->real_escape_string($_POST['password']);  <br/>

$sql = "SELECT * FROM users WHERE username='$username';";  <br/>
$result = mysqli_query($conn, $sql);  <br/>
$row = mysqli_fetch_array($result,MYSQLI_ASSOC);  <br/>

if($row){  <br/>
    echo '$row = true';
}
else{
    echo '$row = false';
}

while($row) {
    echo 'Fetched result<br/>';
    if($row['username'] == $username){
        echo 'Found user in database';
        if(password_verify($password, $row['password'])){
            echo 'Successfull login';
            header('Location: home.html');
            exit;
        }
        else{
            echo 'Wrong password';
        }
    }
    else {
        echo 'Could not find user';  <br/>
    }
}

<?php

include_once 'includes/dbh.php';

$sql = "SELECT * FROM users;";
$result = mysqli_query($conn, $sql);
$resultCheck = mysqli_num_rows($result);

if($resultCheck > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        if($row['username'] == $username){
            // Note: Add message username already taken in error session
             echo 'Username already taken';
             exit;
        }
    }
}


$username = $conn->real_escape_string($_POST['username']);
$password = $conn->real_escape_string($_POST['password']);
$password = password_hash($password, PASSWORD_DEFAULT, ['cost' => 12]);
$email = $conn->real_escape_string($_POST['email']);
$sql = "INSERT INTO users (username, password, email, points)" . "VALUES ('$username', '$password', '$email', '0')";

if($conn->query($sql) === true){
    header('Location: index.html');
    exit;
}
else {
    echo 'Error while signing up!';
}