"Undefined index" warning in vip-caching.php

[gmazzap]

The function wpcom_vip_maybe_skip_old_slug_redirect (https://github.com/Automattic/vip-go-mu-plugins/blob/master/vip-helpers/vip-caching.php#L712-L720) in our local environment produces a warning: Undefined index: DOCUMENT_URI.

In our systems, the server variable DOCUMENT_URI is not defined, we have the same value in REQUEST_URI, instead.

This might not be an issue on VIP servers, but should be took into account for local environements. This is filling our local logs as it happens at every frontend request.

Considering that min PHP version is now 7.2, I would suggest something like this:

$uri = $_SERVER['DOCUMENT_URI'] ?? $_SERVER['REQUEST_URI'] ?? null;

// We look to see if a malformed url (represented by 'http:' ) is right after the starting / in DOCUMENT_URI hence position 1
if ( is_404() && ( 1 === strpos( $uri, 'http:' ) || 1 === strpos( $uri, 'https:' ) ) ) {

which is both readable and fix the issue.

An alternative could be using add_query_arg() function so avoid direct access to $_SERVER values at all.

It worth nothing that add_query_arg() uses REQUEST_URI not DOCUMENT_URI.

[GaryJones]

@gmazzap Thanks for your patience!