Is it possible to modify the default YouTube embed attributes string?

Question

I'd like to suppress related YouTube videos by appending '&rel=0' to the string of embed attributes output to the video iframe in my post.

I believe this requires a filter that modifies the $attr array before it is passed to wp_embed_handler_youtube() (located in wp-includes/media.php).

Assuming I'm on the right track, is there a way to add a filter to my child theme to accomplish this?

Thanks in advance for your help!

---

Ok, so I'm still pretty lost... here is the code in my functions.php:

function modify_YT_embed_attributes($embed, $attr, $url, $rawattr) {  
    $attr["rel"] = "0"; //modify the attributes array
    return $embed; 
}    
add_filter('wp_embed_handler_youtube', 'modify_YT_embed_attributes', 10, 4);

Still not working. What is the obvious thing I'm missing?

Answer 1

There is a filter with the same name as the function wp_embed_handler_youtube

https://developer.wordpress.org/reference/hooks/wp_embed_handler_youtube/

add_filter('wp_embed_handler_youtube', 'ehy_callback', 10, 4);

function ehy_callback($embed, $attr, $url, $rawattr){

   //make necessary changes here
   return $embed;
}

You can add the code in functions.php of your child theme.