Fatal error: Call to undefined function checkLogin() in C:\xampp\htdocs\book_club\members\index.php on line 3

<?php
require_once( "../common.inc.php" );
checkLogin();
displayPageHeader( "Welcome to the Members's Area", true );
?>

<p>Welcome, <?php echo $_SESSION["member"]->getValue( "firstName" ) ?>!
please choose an option below:</p>

<ul>
<li><a href="diary.php">Upcoming events</a></li>
<li><a href="book.php">Current reading list</a></li>
<li><a href="contact.php">Contact the book club</a></li>
<li><a href="logout.php">Logout</a></li>
</ul>

<?php displayPageFooter(); ?>