Untitled

<!DOCTYPE html>
<html>
<body>

<?php
$servername = "localhost:3306";
$username = "root";
$password = "";
$dbname = "university";

$conn = null;
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
} catch (PDOException $e) {
    die('Connection failed: ' . $e->getMessage());
}

$groupId = $firstName = $lastName = $facultyNumber = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {
  $groupId = modify_input($_POST["groupId"]);
  $firstName = modify_input($_POST["firstName"]);
  $lastName = modify_input($_POST["lastName"]);
  $facultyNumber = modify_input($_POST["facultyNumber"]);

	$errors = array();

	if(empty($groupId)) {
		array_push($errors,"Group is required");
	}
	elseif (!ctype_digit($groupId)) {
		array_push($errors,"Group has invalid value");
		$groupId = "";
	}
	if(empty($firstName)) {
		array_push($errors,"First name is required");
	}
	if(empty($lastName)) {
		array_push($errors,"Last name is required");
	}
	if(empty($facultyNumber)) {
		array_push($errors,"Faculty number is required");
	}
	elseif (!ctype_digit($facultyNumber)) {
		array_push($errors,"Faculty number has invalid value");
		$facultyNumber = "";
	}

	if (count($errors) > 0) {
		echo '<ul style="color: red;">';
		foreach ($errors as $error) {
			echo "<li>$error</li>";
		}
		echo '</ul>';
	}
	else {
		$queryStudents = $conn->prepare("INSERT INTO `students` (`FIRST_NAME`, `LAST_NAME`, `FACULTY_NUMBER`, `GROUP_ID`) VALUES (:firstName, :lastName, :facultyNumber, :groupId)");
		$queryStudents->bindParam(':firstName', $firstName);
		$queryStudents->bindParam(':lastName', $lastName);
		$queryStudents->bindParam(':facultyNumber', $facultyNumber);
		$queryStudents->bindParam(':groupId', $groupId);
		$queryStudents->execute();
		header("Location:university.php");
	}
}

function modify_input($data) {
  $data = trim($data);
  $data = stripslashes($data);
  $data = htmlspecialchars($data);
  return $data;
}
?>

<form action="create.php" method="post">
  First name:<br>
  <input type="text" name="firstName" value="<?php echo $firstName;?>">
	<br>
  Last name:<br>
  <input type="text" name="lastName" value="<?php echo $lastName;?>">
	<br>
  Faculty number:<br>
  <input type="text" name="facultyNumber" value="<?php echo $facultyNumber;?>">
	<br>
  Group:<br>
  <select name="groupId">
		<option value="">Please choose</option>
		<?php
		$query = "SELECT groups.id, groups.name, majors.name as major_name FROM groups
							INNER JOIN majors on groups.major_id = majors.id";
		$result = $conn->query($query);
		if ($result->rowCount() > 0) {
				while($row = $result->fetch(PDO::FETCH_ASSOC)) {
						echo '<option value="'.$row["id"].'"';
						if($row["id"] == $groupId) {
							echo ' selected';
						}
						echo '>'.$row["major_name"].': '.$row["name"].'</option>';
				}
		}
		?>
	</select>
	<br><br>
	<input type="submit" value="Submit">
</form>

</body>
</html>