so, your trying to set the default tweet text?
the data-text parameter is only available to Javascript tweet button.
using standard image tweet buttons, you need to pass the text as a parameter to the share link:
<a href="https://twitter.com/share?url=<?php echo urlencode(((!empty($_SERVER["HTTPS"])) ? "https://" : "http://") . $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"]); ?>&text=Check out Broker South in Vicksburg, MS" target="_blank">
tweet-button