my-messages.php

<?php
include ('./classes/DB.php');
include ('./classes/Login.php');
if (Login::isLoggedIn()) {
    $userid = Login::isLoggedIn();
} else {
    die('Not logged in');
}
if (isset($_GET['mid'])) {
    $message = DB::query('SELECT * FROM messages WHERE id=:mid AND (receiver=:receiver OR sender=:sender)', array(':mid' => $_GET['mid'], ':receiver' => $userid, ':sender' => $userid)) [0];
    echo '<h1>View Message</h1>';
    echo htmlspecialchars($message['body']);
    echo '<hr />';
    if ($message['sender'] == $userid) {
        $id = $message['receiver'];
    } else {
        $id = $message['sender'];
    }
    DB::query('UPDATE messages SET `seen`=1 WHERE id=:mid', array(':mid' => $_GET['mid']));
?>
    <form action="send-message.php?receiver=<?php echo $id; ?>" method="post">
        <textarea name="body" rows="8" cols="80"></textarea>
        <input type="submit" name="send" value="Send Message">
    </form>
    <?php
    } else {
?>
        <h1>My Messages</h1>
        <?php
    $messages = DB::query('SELECT messages.*, users.username FROM messages, users WHERE (receiver=:receiver OR sender=:sender) AND users.id = messages.sender', array(':receiver' => $userid, ':sender' => $userid));
    foreach ($messages as $message) {
        if (strlen($message['body']) > 10) {
            $m = substr($message['body'], 0, 10) . " ...";
        } else {
            $m = $message['body'];
        }
        if ($message['seen'] == 0) {
            echo "<a href='my-messages.php?mid=" . $message['id'] . "'><strong>" . $m . "</strong></a> sent by " . $message['username'] . '<hr />';
        } else {
            echo "<a href='my-messages.php?mid=" . $message['id'] . "'>" . $m . "</a> sent by " . $message['username'] . '<hr />';
        }
    }
}
?>