Placeholder in HTML editor text area?

Question

I am trying to make a placeholder appear on the default html editor on a specific post type. The code looks like this:

add_filter('the_editor','add_placeholder_event');
function add_placeholder_event( $html ){
if ( 'event' == $post->post_type )
    $html = preg_replace('/<textarea/', '<textarea placeholder="my place holder text" ', $html);
return $html;
}

It does not work, however, if I remove if ( 'event' == $post->post_type ) from the code it will work (but will apply to every html text editor on Wordpress).

Any idea what I am doing wrong?

Answer 1

Solved it:

function add_placeholder_event( $html ){
$screen = get_current_screen();
$post_type = $screen->post_type;

if( $post_type == 'event' ) {
    $html = preg_replace('/<textarea/', '<textarea placeholder="John Doe" ', $html);
}
return $html;
}
add_filter('the_editor','add_placeholder_event');