Fixes PHP notices related to comments

[stodorovic]

Fixes #385

[stodorovic]

@donnchawp I'm not sure that's the best way, but it seems as readable code without a lot of changes:

defined( 'DONOTDELETECACHE' ) or define( 'DONOTDELETECACHE', 1 );

Related to if ( $_GET[ 'delete_all' ] != 'Empty Trash' && $_GET[ 'delete_all2' ] != 'Empty Spam' ), it's pretty outdated. It depends on language:

French - $_GET[ 'delete_all' ] = "Vider la corbeille"

WP uses (from 3.0 to 4.8) this condition:

if ( isset( $_REQUEST['delete_all'] ) || isset( $_REQUEST['delete_all2'] ) )

[stodorovic]

For first iteration, I decided to add at the begin of function wp_cache_get_postid_from_comment:

if ( defined( 'DONOTDELETECACHE' ) ) {
        return;
}

[donnchawp]

Return the post_id?

[donnchawp]

Looks great and definitely improves that function, but it should return the post ID those two times it returns early.

[stodorovic]

Function wp_cache_get_postid_from_comment is triggering only from couple actions.

wp-cache-phase2.php:  add_action('trackback_post', 'wp_cache_get_postid_from_comment', 99);
wp-cache-phase2.php:  add_action('pingback_post', 'wp_cache_get_postid_from_comment', 99);
wp-cache-phase2.php:  add_action('comment_post', 'wp_cache_get_postid_from_comment', 99);
wp-cache-phase2.php:  add_action('edit_comment', 'wp_cache_get_postid_from_comment', 99);
wp-cache-phase2.php:  add_action('wp_set_comment_status', 'wp_cache_get_postid_from_comment', 99, 2);

I've checked it with xdebug and it seems that this function only define constant DONOTDELETECACHE. I don't see the code which uses post_id which is returned from function. Maybe we can remove all values from return. Also we could move this function into new function wpsc_...... (then we can add deprecation notice for current function if other plugin uses it).

https://developer.wordpress.org/reference/hooks/trackback_post/
https://developer.wordpress.org/reference/hooks/pingback_post/
https://developer.wordpress.org/reference/hooks/comment_post/
https://developer.wordpress.org/reference/hooks/edit_comment/
https://developer.wordpress.org/reference/hooks/wp_set_comment_status/

I just checked again and all hooks are actions. So, it makes sense to we totally remove return post_id (and probably reorganize the code) in the future. We should think over about it.

Anyway, I'll try to add post_id now to we keep compatibility with legacy code.

[donnchawp]

Return the post_id?

[donnchawp]

You're right! Thanks for checking. I think that function should be renamed in the future so it's obvious it's not returning something. I had forgotten that.

I'll merge this code as-is. We can see about further improvements later. Thanks!