In classic WordPress themes, you can put this code in your functions.php file, then you can add php code directly into Text widgets.
function php_in_widgets($html){
if(strpos($html,"<"."?php")!==false){
ob_start(); eval("?".">".$html);
$html=ob_get_contents();
ob_end_clean();
}
return $html;
}
add_filter('widget_text','php_in_widgets',100);
For example:
Note that you’ll want to be sure to use the [Text] tab, not [Visual].
