registrieren.php

    <div class="box">

          <h2>Registrieren</h2>

          <form class="registrieren" action="includes/registrieren.inc.php" method="post">
              <input type="text" name="uid" placeholder="Benutzername">
              <input type="text" name="mail" placeholder="E-Mail">
              <input type="password" name="pwd" placeholder="Passwort">
              <input type="password" name="pwd-repeat" placeholder="Passwort wiederholen">
              <button type="submit" name="registrieren-submit">Registrieren</button>
          </form>

    </div><!--end .box-->


registrieren.inc.php


if(isset($_POST['registrieren-submit'])){

      // incl. DB connection
      include "db.php";


      //Übergabe POST registrieren.php  , POST
      $username = $_POST['uid'];
      $email = $_POST['mail'];
      $password = $_POST['pwd'];
      $passwordRepeat = $_POST['pwd-repeat'];

      // Prüfe ob INPUT befüllt und Valide
      if(empty($username) || empty($email) || empty($password) || empty($passwordRepeat)){
          header("Location: ../registrieren.php?error=emptyfields&uid=".$username."&mail=".$email);
          exit();
      }
      else if(!filter_var($email, FILTER_VALIDATE_EMAIL)){
          header("Location: ../registrieren.php?error=invalidmail&uid=".$username);
          exit();
      }
      else if(!preg_match("/^[a-zA-Z0-9]*$/", $username)){
          header("Location: ../registrieren.php?error=invalidmail&uid=".$email);
          exit();
      }
      else if ($password !==$passwordRepeat){
          header("Location: ../registrieren.php?error=passwordcheck&uid=".$username."&email=".$email);
          exit();
      }
      else {

        $sql  = "SELECT uidUsers FROM users WHERE uidUsers=?";
        $stmt = mysqli_stmt_init($mysqli);
        if(!mysqli_stmt_prepare($stmt, $sql)){
            header("Location: ../registrieren.php?error=sqlerror");
            exit();
        }
        else{
            mysqli_stmt_bind_param($stmt, "s", $username);
            mysqli_stmt_execute($stmt);
            mysqli_stmt_store_result($stmt);
            $resultCheck = mysqli_stmt_num_rows($stmt);
            if($resultCheck > 0){
              header("Location: ../registrieren.php?error=usertaken&email=".$email);
              exit();
            }
            else{
                $sql = "INSERT INTO users (uidUsers, emailUsers, pwdUsers) VALUES (?, ?, ?) ";
                $stmt = mysqli_stmt_init($mysqli);
                if(!mysqli_stmt_prepare($stmt, $sql)){
                  header("Location: ../registrieren.php?error=sqlerror");
                  exit();
                }
                else{
                    $hashedPwd = password_hash($password, PASSWORD_DEFAULT);

                    mysqli_stmt_bind_param($stmt, "sss", $username, $email, $hashedPwd);
                    mysqli_stmt_execute($stmt);
                    header("Location: ../registrieren.php?signup=success");
                    exit();
                }

            }
        }

      }
      mysqli_stmt_close($stmt);
      mysqli_close($mysqli);

}
else{
    header("Location: ../index.php");
    exit();

}


/*
Soweit funktioniert alles
*/



////////////////

Login.php

  <div class="box">
        <h2>Login System  </h2>
        <?php echo $msg;  ?>
        <form class="login" action="includes/login.inc.php" method="post">
            <input type="text" name="mailuid" placeholder="Benutzername oder E-Mail...">
            <input type="password" name="pwd" placeholder="Passwort">
            <button type="submit" name="login-submit">Einloggen</button>
        </form>

        <a href="registrieren.php">Registrieren</a>

        <form class="logout" action="includes/logout.inc.php" method="post">
              <button type="submit" name="logout-submit">Ausloggen</button>
        </form>

    </div><!--end .box-->


login.inc.php

if(isset($_POST['login-submit'])){

        // incl. DB connection
        include "db.php";

       $mailuid = $_POST['mailuid'];
       $password = $_POST['pwd'];


        if(empty($mailuid) || empty($password)){
            header("Location: ../index.php?error=emtyfields");
            exit();
        }
        else{
            $sql = "SELECT * FROM users WHERE uidUsers=? OR emailUsers=?";
            $stmt = mysqli_stmt_init($mysqli);
            if(!mysqli_stmt_prepare($stmt, $sql)){
                header("Location: ../index.php?error=sqlerror");
                exit();
            }
            else{

                mysqli_stmt_bind_param($stmt, "ss" , $mailuid, $password );
                mysqli_stmt_execute($stmt);
                $result = mysqli_stmt_get_result($stmt);

                if($row = mysqli_fetch_assoc($result)){  /*Fehler : evtl hier?*/

                        $pwdCheck = password_verify($password, $row['pwdUsers']);


                        if($pwdCheck == false){

                           header("Location: ../index.php?error=wrongpwd");
                           exit();
                        }
                        else if ($pwdCheck == true){

                              session_start();
                              $_SESSION['userId'] = $row['idUsers'];
                              $_SESSION['userUId'] = $row['uidUsers'];

                              header("Location: ../index.php?login=success");
                              exit();
                        }

                }else{
                  header("Location: ../index.php?error=nouser");
                  exit();

                }
            }
        }


      }
      else{

        header("Location: ../index.php");
        exit();
}