LoginClass

<?php

    class LoginManager {

        var $PDOObject;
        var $AccountTable;
        var $UserField;
        var $PasswordField;
        var $User;
        var $Credentials;
        var $DBLoginReturn;
        var $ExistingUser;

        // Create PDO Object, Assign AccountTable, User Field, Password Field
        function SetDB($sHost, $sDatabase, $sUsername, $sPassword, $sAccountTable, $sUserField, $sPasswordField) {
            $this->PDOObject = new PDO("mysql:host=$sHost;dbname=$sDatabase", $sUsername, $sPassword);
            $this->AccountTable = $sAccountTable;
            $this->UserField = $sUserField;
            $this->PasswordField = $sPasswordField;
        }

        // Set Username/Email
        function SetUser($sUser) {
            $this->User = $sUser;
        }

        //
        function SetCredentials($sCredentials) {
            $this->Credentials = $sCredentials;
        }

        // Verify Encrypted Credentials
        function VerifyCredentials($sPlainTextPass) {
            $this->PlainCredentials = $sPlainTextPass;

            if(password_verify($this->PlainCredentials, $this->DBLoginReturn[0][$this->PasswordField])) {
                return true;
            } else {
                return false;
            }
        }

        // Try Login
        function GetLoginDB() {
            try {
                $sDBConn = $this->PDOObject->prepare("SELECT $this->UserField, $this->PasswordField FROM $this->AccountTable WHERE $this->UserField = :loginuser");
                $sDBConn->execute(array(
                    "loginuser" => $this->User
                    ));
                $this->DBLoginReturn = $sDBConn->fetchAll(PDO::FETCH_ASSOC);

            } catch(Exception $loginerror) {
                return var_dump($loginerror);
            }
        }

        // Set Session Variables
        function SetSessionVariables() {
            $_SESSION['loggedin'] = true;
            $_SESSION['user'] = $this->User;
        }

        function CheckUserExists($sUser) {
            $this->ExistingUser = $sUser;
            $sDBConn = $this->PDOObject->prepare("SELECT $this->UserField FROM $this->AccountTable WHERE $this->UserField = :username");
            $sDBConn->execute(array(
                "username" => $this->User
            ));

            if($sDBConn->rowCount() >= 1) {
                return true;
            } else {
                return false;
            }
        }

        // Register User
        function RegisterUser($sFirstname, $sLastname, $sTime) {

            try {
            $sDBConn = $this->PDOObject->prepare("INSERT INTO $this->AccountTable (username, password, firstname, lastname, epoch) VALUES (:username, :password, :firstname, :lastname, :epoch)");
            $sDBConn->execute(array(
                "username" => $this->User,
                "password" => $this->Credentials,
                "firstname" => $sFirstname,
                "lastname" => $sLastname,
                "epoch" => $sTime
            ));
            } catch(Exception $registererror) {
                return var_dump($registererror);
            }
        }

        function EncryptPass($sPassword) {

            $sOptions = [
                'cost' => 12,
            ];

            $sHash = password_hash($sPassword, PASSWORD_BCRYPT, $sOptions);

            return $sHash;
        }
    }

?>

Example Register Form

<?php

require_once('loginmanager.php');

if(isset($_POST['email']) && isset($_POST['password']) && isset($_POST['firstname']) && isset($_POST['lastname'])) {

// Declare Login Manager Class
$vManager = new LoginManager;

// New Database PDO Object
$sPDO = $vManager->SetDB('localhost', 'users', 'sanquin', 'alloy', 'accounts', 'Username', 'Password');

// ##### Register Time #####

// Set User
$vManager->SetUser($_POST['email']);

// Encrypt Pass and Get a return
$vEncryptedPass = $vManager->EncryptPass($_POST['password']);

// Set Credentials
$vManager->SetCredentials($vEncryptedPass);

// Register User Firstname, Lastname, Time.
$vManager->RegisterUser($_POST['firstname'], $_POST['lastname'], time());

echo "user registered";
} else {
    echo "Not All Forms Filled In";
}
?>

<form action="register.php" method="POST">
    <input type="text" name="email" placeholder="Email..."/><br>
    <input type="text" name="password" placeholder="Password..."/><br>
    <input type="text" name="firstname" placeholder="Firstname..."/><br>
    <input type="text" name="lastname" placeholder="Lastname..."/><br>
    <input type="submit" value="Submit"/>
</form>

Example Login Form

<?php
session_start();

require_once('loginmanager.php');

if(isset($_POST['email']) && isset($_POST['password'])) {

// Declare Login Manager Class
$vManager = new LoginManager;

// New Database PDO Object
$sPDO = $vManager->SetDB('localhost', 'userdb', 'sanquin', 'test', 'accounts', 'username', 'password');

// ##### Login Time #####
$vManager->SetUser($_POST['email']);

$vManager->GetLoginDB();

// Password will be the post of their pass
if($vManager->VerifyCredentials($_POST['password'])) {
    $vManager->SetSessionVariables();
    die("<script>location.href = './loggedin.php'</script>");
}

} else {
    echo "Login Failed";
}
?>

<form action="login.php" method="POST">
    <input type="text" name="email" placeholder="Email..."/><br>
    <input type="text" name="password" placeholder="Password..."/><br>
    <input type="submit" value="Submit"/>
</form>