How to safely output HTML from a PHP program?
You always want to HTML-encode things inside HTML attributes, which you can do with htmlspecialchars: <span title=”<?php echo htmlspecialchars($variable); ?>”> You probably want to set the second parameter ($quote_style) to ENT_QUOTES. The only potential risk is that $variable may already be encoded, so you may want to set the last parameter ($double_encode) to false.