functions.php

<?php
//koneksi ke database
$conn = mysqli_connect("localhost", "root", "", "dbpkendaraan");

function query($query) {
    global $conn;
    $result = mysqli_query($conn, $query);
    $rows = [];
    while ( $row = mysqli_fetch_assoc($result) ){
        $rows[] = $row;
    }
    return $rows;
}

function registrasi($data){
    global $conn;

    $username = strtolower(stripslashes($data['username']));
    $email = strtolower(stripslashes($data['email']));
    $password = mysqli_real_escape_string($conn, $data['password']);
    $password2 = mysqli_real_escape_string($conn,$data['password2']);

    //cek username sudah ada atau belum
    $result = mysqli_query($conn, "SELECT username FROM user WHERE username= '$username'");
    if (mysqli_fetch_assoc($result) ){
        echo "<script>
        alert('username sudah ada!');
        </script>";
        return false;
    }

    //cek konfirmasi password
    if( $password !== $password2){
        echo "<script>
        alert('konfirmasi password tidak sesuai!');
        </script>";
        return false;
    } 

    // enkripsi password
    $password = password_hash($password, PASSWORD_DEFAULT);

    // tambahkan user baru ke database
    mysqli_query($conn, "INSERT INTO user VALUES('', '$username', '$email','$password')");

    return mysqli_affected_rows($conn);
}

?>