enforce a consistent home and siteurl www. pref

[Denis-de-Bernardy]

Seen on a few sites. home and siteurl with inconsistent www prefs prevents the admin user's cookie from getting picked up properly, upon logging in.

code I currently use to prevent the issue is this:

add_action('login_head', 'fix_www_pref');

function fix_www_pref() {
	$home_url = get_option('home');
	$site_url = get_option('siteurl');
		
	$home_www = strpos($home_url, '://www.') !== false;
	$site_www = strpos($site_url, '://www.') !== false;
		
	if ( $home_www != $site_www ) {
		if ( $home_www )
			$site_url = str_replace('://', '://www.', $site_url);
		else
			$site_url = str_replace('://www.', '://', $site_url);
		update_option('site_url', $site_url);
	}
} # fix_www_pref()

there's probably a better way and a better location for this.

[Denis-de-Bernardy]

punting pending patch

[Denis-de-Bernardy]

see also #10095 (closed issue), which highlights a side-effect

[Denis-de-Bernardy]

see also #10447 for more potential side effects

[hakre]

Related: #10970

[scribu]

Related: #11945

[nacin]

Closed #20430 as a duplicate.

[SergeyBiryukov]

Crops up on support forums once in a while.

[norcross]

catch $_POST values for urls and check / replace if needed

[helenyhou]

Version number indicates when the bug was initially introduced/reported.

[johnpbloch]

Explicit COOKIE_DOMAIN for www inconsistency

[johnpbloch]

It seems to me that overriding a user's chosen preference in the options table is the wrong way to fix this bug. Since the problem is that it causes inconsistencies in cookie behavior, it makes more sense to me to fix this issue by forcing a value for COOKIE_DOMAIN if a www. inconsistency is detected.

[johnbillion]

I struggle to believe that this is such a common occurrence that core needs to handle this.

In addition, both of the proposed solutions will break sites which use a different domain name for home and siteurl (eg. www.example.com and admin.example.com).

Feel free to re-open if there's a common situation which leads to this that I'm not accounting for, and/or if someone wants to write a comprehensive patch with unit tests.