Is this PHP code secure?
<p>Just a quick question: is the following PHP code secure? Also is there anything you think I could or should add?</p>

<pre><code>    $post = $_GET['post'];

    if(is_numeric($post))
    {
        $post = mysql_real_escape_string($post);
    }
    else
    {
        die("NAUGHTY NAUGHTY");
    }

    mysql_select_db("****", $*****);

    $content = mysql_query("SELECT * FROM tbl_***** WHERE Id='" . $post . "'");
</code></pre>
