ob_start include config php function escape text return mysql_real_esc

<?
ob_start();
include "config.php";

function escape($text) {
    return mysql_real_escape_string(htmlspecialchars($text, ENT_QUOTES));
}

$comment = isset($_POST['comment']) ? escape($_POST['comment']) : null;

if ($_POST) {
    mysql_query("insert into chat(messages) values('$comment')");
    header('Location: /');
}

$q = mysql_query("select * from chat ORDER BY `id` DESC limit 10");

while($a = mysql_fetch_assoc($q)) {
    echo $a['messages'].'<br />';
}

echo '
<form method="post">
    <input name="comment" autofocus>
    <input type="submit">
</form>
';

ob_end_flush();