<?php
if(isset($_POST['username'], $_POST['password'])){
 $username = htmlspecialchars($_POST['username']);
 $password = password_hash(htmlspecialchars($_POST['password']), PASSWORD_DEFAULT);


$login_statetment = $pdo->prepare("SELECT * FROM user_users WHERE username LIKE :username OR email LIKE :username");
$login_statetment->bindParam("username", $username);
$login_statetment->execute();
$user = $login_statetment->fetch();

  if($user != null) {
    if(isset($_SESSION)){
      session_start();
    }
    $_SESSION['username'] = $user['username'];
      header("Location: ?a=loggedin");
  } else {
      echo ('<div class="alert alert-danger" role="alert">Deine Passwörter stimmen nicht überein!</div>');
  }
}

?>
<form class="col-md-6 offset-md-3" method="post" action="?p=login">
<div class="form-group">
  <label>Benutzername oder Email</label>
  <input type="text" class="form-control" name="username" required >
</div>
<form class="col-md-6 offset-md-3">
  <div class="form-group">
    <label>Passwort</label>
    <input type="password" class="form-control" name="email" required >
  </div>
  <form class="col-md-6 offset-md-3">
    <div class="form-group">
      <input type="submit" class="btn btn-outline-primary" value="Anmelden">
    </div>
</form>