What hook should I use that will fire whenever I open a post for editing in the WP back-end?

Question

I'd like to create a simple action hook that fires whenever I open a post for editing in the WordPress back-end. What hook(s) can/should I use for this? The action would just be a simple echo command that prints text to the screen (as this is only for testing purposes).

Thanks.

Answer 1

Don't what you want to do but here is something that I did earlier on editor page of post type.

function wpb_change_title_text( $title ){
    $screen = get_current_screen();

    if  ( 'post' == $screen->post_type ) {                //Specify post type
        $title = 'New Placeholder text will come here ';  //Enter new placeholder text
    }

    return $title;
}

add_filter( 'enter_title_here', 'wpb_change_title_text' );

This function will change placeholder text of title textbox of any post type, here I am changing text of post (dashboard -> add post).