If you want to be able to use PHP snippet in the Text Widget place the following snippet in the functon.php file.

 

function phpinwidget($text) {
 if (strpos($text, '<' . '?') !== false) {
 ob_start();
 eval('?' . '>' . $text);
 $text = ob_get_contents();
 ob_end_clean();
 }
 return $text;
}
add_filter('widget_text', 'phpinwidget', 99);