function find_selected_pages($public = false)
{
    global $current_subject;
    global $current_page;
    if (isset($_GET["subject"])) {
        //use get request to get my subject id
        $selected_subject_id = $_GET["subject"];
        //get my subject details by id from the database
        $current_subject = find_subject_by_id($selected_subject_id, $public);
        $selected_page_id = null;
        if ($current_subject && $public) {
            $current_page = find_default_page_for_subject($current_subject["id"]);
        } else {
            $current_page = null;
        }
    } elseif (isset($_GET["page"])) {
        $selected_subject_id = null;
        $current_subject = null;
        $selected_page_id = $_GET["page"];
        $current_page = find_page_by_id($selected_page_id);
    } else {
        $selected_subject_id = null;
        $current_subject = null;
        $selected_page_id = null;
        $current_page = null;
    }
}

function find_selected_page()
{
    global $current_subject;
    global $current_page;
    if (isset($_GET["subject"])) {
        $current_subject = find_subject_by_id($_GET["subject"]);
        $current_page = null;
    } elseif (isset($_GET["page"])) {
        $current_subject = null;
        $current_page = find_page_by_id($_GET["page"]);
    } else {
        $current_subject = null;
        $current_page = null;
    }
}

function find_selected_page($public = false)
{
    global $current_subject;
    global $current_page;
    if (isset($_GET["subject"])) {
        $current_subject = find_subject_by_id($_GET["subject"], $public);
        if ($current_subject && $public) {
            $current_page = find_default_page_for_subject($current_subject["id"]);
        } else {
            $current_page = null;
        }
    } elseif (isset($_GET["page"])) {
        $current_page = find_page_by_id($_GET["page"], $public);
        $current_subject = null;
    } else {
        $current_subject = null;
        $current_page = null;
    }
}

<?php

require_once "../includes/session.php";
require_once "../includes/db_connection.php";
require_once "../includes/functions.php";
confirm_logged_in();
?>

<?php 
$current_subject = find_subject_by_id($_GET["subject"], false);
if (!$current_subject) {
    // subject ID was missing or invalid or
    // subject couldn't be found in database
    redirect_to("manage_contenct.php");
}
$pages_set = find_pages_for_subject($current_subject["id"]);
if (mysqli_num_rows($pages_set) > 0) {
    $_SESSION["message"] = "Can't delete a subject with pages.";
    redirect_to("manage_content.php?subject={$current_subject["id"]}");
}
$id = $current_subject["id"];
$query = "DELETE FROM subjects WHERE id = {$id} LIMIT 1";
$result = mysqli_query($connection, $query);
if ($result && mysqli_affected_rows($connection) == 1) {
    // Success
    $_SESSION["message"] = "Subject deleted.";
    redirect_to("manage_content.php");
} else {
    // Failure
    $_SESSION["message"] = "Subject deletion failed.";
    redirect_to("manage_content.php?subject={$id}");

<?php

require_once "../includes/session.php";
require_once "../includes/db_connection.php";
require_once "../includes/functions.php";
?>

<?php 
$current_subject = find_subject_by_id($_GET["subject"]);
if (!$current_subject) {
    // subject ID was missing or invalid or
    // subject couldn't be found in database
    redirect_to("manage_content.php");
}
$pages_set = find_pages_for_subject($current_subject["id"], false);
if (mysqli_num_rows($pages_set) > 0) {
    $_SESSION["message"] = "Can't delete a subject with pages.";
    redirect_to("manage_content.php?subject={$current_subject["id"]}");
}
$id = $current_subject["id"];
$query = "DELETE FROM subjects WHERE id = {$id} LIMIT 1";
$result = mysqli_query($connection, $query);
if ($result && mysqli_affected_rows($connection) == 1) {
    // Success
    $_SESSION["message"] = "Subject deleted.";
    redirect_to("manage_content.php");
} else {
    // Failure
    $_SESSION["message"] = "Subject deletion failed.";
    redirect_to("manage_content.php?subject={$id}");
}

function find_selected_page($public = false)
{
    global $current_page;
    global $current_subject;
    if (isset($_GET["subject"])) {
        //  This is an associative array with all the database info
        $current_subject = find_subject_by_id($_GET["subject"], $public);
        if ($current_subject && $public) {
            $current_page = find_default_page_for_subject($current_subject["id"]);
        } else {
            $current_page = null;
        }
    } elseif (isset($_GET["page"])) {
        $current_subject = null;
        $current_page = find_page_by_id($_GET["page"], $public);
    } else {
        $current_page = null;
        $current_subject = null;
    }
}

    $selected_page_id = null;
}
?>
<div id="main">
  <div id="navigation">
		<?php 
echo navigation($selected_subject_id, $selected_page_id);
?>
  </div>
  <div id="page">
		<?php 
if ($selected_subject_id) {
    ?>
	    <h2>Manage Subject</h2>
			<?php 
    $current_subject = find_subject_by_id($selected_subject_id);
    ?>
			Menu name: <?php 
    echo $current_subject["menu_name"];
    ?>
<br />
			
		<?php 
} elseif ($selected_page_id) {
    ?>
			<h2>Manage Page</h2>
			<?php 
    $current_page = find_page_by_id($selected_page_id);
    ?>
			Menu name: <?php 
    echo $current_page["menu_name"];

function find_selected_page($public = false)
{
    global $current_subject;
    global $current_page;
    //instead of returning we can make it as a global variable
    if (isset($_GET["subject"])) {
        $current_subject = find_subject_by_id($_GET["subject"], $public);
        if ($current_subject && $public) {
            $current_page = default_page_for_subject($current_subject["id"]);
            # default page for subject		}
        } else {
            $current_page = null;
        }
    } elseif (isset($_GET["page"])) {
        $current_page = find_page_by_id($_GET["page"], $public);
        # for not displaying the invisible pages
        $current_subject = null;
    } else {
        # for coming from admin page
        $current_subject = null;
        $current_page = null;
    }
}

function find_selected_page()
{
    global $current_subject;
    // creating them in the global scope
    global $current_page;
    // creating them in the global scope
    if (isset($_GET["subject"])) {
        $current_subject = find_subject_by_id($_GET["subject"]);
        $current_page = null;
    } elseif (isset($_GET["page"])) {
        $current_page = find_page_by_id($_GET["page"]);
        $current_subject = null;
    } else {
        $current_subject = null;
        $current_page = null;
    }
}