Adding code before post title with the_title produces weird results

Question

add_action ('the_title' , 'test'); 

function test($title) {

    $mycode = '<div>test</div>';

    echo $mycode . $title;

 }

I expected this functions.php code to add "test" before the post title. It does that. But it adds it also all over the place on the page. Not sure what's the logic, it seems it adds appends it to all menu items of the page.

Am I wrong on my usage of the_title? Or might there be theme interference here?

Answer 1

the_title filter has two parameters passed to it, $title and $id. You could use the $id to check the current post type and then do stuff based on that.

add_action ('the_title' , 'test', 10, 2);
function test($title, $id) {
  return 'post' === get_post_type($id) ? '<div>test</div> ' . $title : $title;
}

The problem with this is that the filter is kind of not aware in which context it is called (naturally WP conditionals provide some context). So you might get unexpected results and end up with the custom title prefix/suffix showing up everywhere on a single view, e.g. the main menu, main title, related posts, sidebar, footer..., even if you just wanted to make the modification in only one part of your view. This of course depends on your setup, needs and use case.