<?php
$select = mysql_fetch_assoc(mysql_query("SELECT * FROM users WHERE rank >= 2"));
mysql_query("UPDATE user_stats SET DailyRespectPoints = '5' WHERE id = '{$select['id']}'");
echo 'Done.';
?>
I don't know if this will work, but that is similar how it should be done.
Then setup a cronjob to run every 24 hours.