redirect_canonical() – Undefined indexes 'host' and 'scheme'

[theamila]

Hello,
We have a problem on our Blog (​http://blog.mila.com). Since over half a year, we get these notifications on top of our wordpress blog:

Notice: Undefined index: HTTP_HOST in /opt/wordpress/wp-includes/canonical.php on line 66
Notice: Undefined index: HTTP_HOST in /opt/wordpress/wp-includes/nav-menu-template.php on line 558

The notifications come and go, so i don't know what the problem is..
This is line 66 in the canonical file:

<?php
$requested_url .= $_SERVER['HTTP_HOST'];

And this is line 558 in nav-menu-template.php:

<?php
$current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_root_relative_current );

We know that the notification is shown because the variable HTTP_HOST is not set, but we don't know how to fix that. It would be great if you could help

[theamila]

canonical.php file

[theamila]

nav menu template file

[swissspidy]

Duplicate of #32229. This is fixed in 4.4.

[theamila]

I have inserted the lines from issue 32229 now i get this error:

Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 424
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 425
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 425
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 426
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 428
Notice: Undefined index: scheme in /opt/wordpress/wp-includes/canonical.php on line 445
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 424
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 425
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 425
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 426
Notice: Undefined index: host in /opt/wordpress/wp-includes/canonical.php on line 428
Notice: Undefined index: scheme in /opt/wordpress/wp-includes/canonical.php on line 445

[swissspidy]

Looks like $redirect['scheme'] and $original['host'] are not correctly set. Those two arrays are returned by parse_url, so it's certainly possible that those keys aren't set.

[itproitserviceflcom]

I have same warnings and found that it was produced by "HEAD" requests. "GET" and "POST" requests doesn't give the warning.

[SergeyBiryukov]

#39880 was marked as a duplicate.

[SergeyBiryukov]

Related: #39827

[Andy Schmidt]

This bug is still littering the log files in v4.9.4, out of the box. Spent time tracking down the cause and was going to report it, now realizing this is a known issue.

In my case, problem is that several times daily, redirect_canonical() is called with $_SERVER[HOST] empty and $_SERVER [URI] = '/'.

As a result $original[host] is never set and the code will eventually fail starting at lines 461 - 463:

<?php
        if ( strtolower($original['host']) == strtolower($redirect['host']) ||
                ( strtolower($original['host']) != 'www.' . strtolower($redirect['host']) && 'www.' . strtolower($original['host']) != strtolower($redirect['host']) ) )
                $redirect['host'] = $original['host'];

It should be trivial to fix at lines 70-73, currently:

<?php
        $original = @parse_url($requested_url);
        if ( false === $original ) {     // <-- this line requires a fix!
                return;
        }

by simply validating that a 'host' was actually set, since the code does expect one later:

<?php
        if ( false === $original or !isset( $original['host'] ) ) {

[Andy Schmidt]

I have confirmed that my proposed fix for 4.9.4 does address this problem. There was no recurrence in the past 4 days, and no ill effects!

Now that a confirmed fix is available, may I suggest moving it from some "future release" milestone to the next update, so that this may be closed after 2 years.

[archon810]

While we're waiting for this fix, I'm also seeing a similar issue in wp-includes/class-wp-http-ixr-client.php.

ErrorException: Undefined index: host
#7 wp-includes/class-wp-http-ixr-client.php(27): handleError
#6 wp-includes/class-wp-http-ixr-client.php(27): __construct
#5 wp-includes/comment.php(2652): pingback
#4 wp-includes/comment.php(2486): do_all_pings
#3 wp-includes/class-wp-hook.php(286): apply_filters
#2 wp-includes/class-wp-hook.php(310): do_action
#1 wp-includes/plugin.php(515): do_action_ref_array
#0 wp-cron.php(126): null

Same for

Undefined index: scheme

Examining the $bits variable, I see this:

bits	
{
    path: /wordpress/xmlrpc.php
}

The function this happens in:

<?php
public function __construct($server, $path = false, $port = false, $timeout = 15) {
                if ( ! $path ) {
                        // Assume we have been given a URL instead
                        $bits = parse_url($server);
                        $this->scheme = $bits['scheme'];
                        $this->server = $bits['host'];
                        $this->port = isset($bits['port']) ? $bits['port'] : $port;
                        $this->path = !empty($bits['path']) ? $bits['path'] : '/';

All such errors are caused by wordpress/wp-cron.php?doing_wp_cron.

Perhaps the fix here can also be applied to class-wp-http-ixr-client.php?

Thank you.

[RavanH]

Not sure if this is completely related or just sounds very similar (involving path, not host or scheme) but I'll share it here as it may help in testing. I've encountered the following on a clean install of WP 4.9.8 with default theme and no plugins activated.

1. Turn WP_DEBUG is on (obviously)
2. Set permalinks to Numeric
3. Visit a non-existent feed by it's plain URL, for example /?feed=sitemap

Notices shown:

PHP Notice:  Undefined index: path in /var/www/html/wp-includes/canonical.php on line 393
PHP Notice:  Undefined index: path in /var/www/html/wp-includes/canonical.php on line 393
PHP Notice:  Undefined index: path in /var/www/html/wp-includes/canonical.php on line 465

You may ask: Why bother with non-existent feeds? Answer: Plugin developers (as I) may add custom feed URLs and will encounter this notice during development (like I did) ... and waste a lot of time trying to find out what is going on ;)

[SergeyBiryukov]

#45254 was marked as a duplicate.

[pento]

This ticket needs a patch and tests.

[Kovah]

Unfortunately this is still an issue in WP 5.1.1 and currently littering our Sentry logs.

As of 5.1.1, line 504 of /wp/wp-includes/canonical.php is throwing the "Undefined index: host" error.
Corresponding code:

    // Ignore differences in host capitalization, as this can lead to infinite redirects
    // Only redirect no-www <=> yes-www
>>> if ( strtolower( $original['host'] ) == strtolower( $redirect['host'] ) ||
       ( strtolower( $original['host'] ) != 'www.' . strtolower( $redirect['host'] ) && 'www.' . strtolower( $original['host'] ) != strtolower( $redirect['host'] ) ) ) {
          $redirect['host'] = $original['host'];
    }

[robbiegod]

FYI, I am running Wordpress 5.2, PHP 7.2. I am seeing this error display just below the body tag.

Notice: Undefined index: path in /wp-includes/canonical.php on line 419

[JochenT]

The reason for these notices are probably the same as I've found for multisites. See #47733 (Undefined index HTTP_HOST in wp-includes/ms-settings.php)

If this is true a more general handling of the HTTP server variables may be needed during the bootstrap/load process.

[Cybr]

This notice happens because HTTP/1.0 doesn't fill the HTTP_HOST index in $_SERVER. HTTP/1.1 and higher do support that index. Alas, around the world, archaic browsers and servers are still using HTTP/1.0.

Because of that, $requested_url isn't populated, and $original = @ parse_url( $requested_url ); won't have anything useful to parse, and won't fill in the host index. Ergo, three notices will pop up when trying to call $original['host'].

I think we can polyfill the $_SERVER['HTTP_HOST'] index early. Doing so would also address #47733. Be mindful of virtual hosts.