How to handle a shortcode function directly?

Question

I was wondering how i can handle a shortcode function directly? At the moment i have created a shortcode which works OK. The shortcode function outputs a image.

Now in functions.php i have another function which needs the output image. I am using the do_shortcode and it works.

$image = do_shortcode('[route_thumb id="'.$post_id.'"]') ;

but how can i call the function directly this one didn't work

 $image = route_thumb_function($atts['id']=$post_id);

Answer 1

Shortcode handler function receives two arguments array $attr and string $content. So to pass attributes to shortcode handler function, just pass it as array:

$image = route_thumb_function( array( 'id' => $post_id ) );