PHP Warning: Invalid argument supplied for foreach() in /wp-cron.php about slickstack

[EdTrojas]

About the error: == PHP Warning: Invalid argument supplied for foreach () in /var/www/html/wp-cron.php==

I found a solution on a Wordpress forum. I´m not a developer, so I don't know if this solution has any harmful effect.
I am testing, monitoring, and waiting for some negative response when changing the WP-CRON.php code

-Is a wp bug, line 117 of wp-cron.php reads: foreach ( $cronhooks as $hook => $keys ) {

-this should read: if ( $cronhooks ) foreach ( $cronhooks as $hook => $keys ) {
or: if ( is_array( $cronhooks ) ) foreach ( $cronhooks as $hook => $keys ) {

-this will prevent warning messages like: [Fri Aug 28 21:15:16.443167 2020] [fcgid:warn] [pid 62430] [client 77.68.64.25:32953] mod_fcgid: stderr: PHP Warning: Invalid argument supplied for foreach() in /home/domains/vol3/578/2510578/user/htdocs/wp-cron.php on line 117, referer: https://www.pakohl.com/wp-cron.php?doing_wp_cron=1598645713.5858569145202636718750

-when $cronhooks is false

The solution was obtained by Jacob N. Breetvelt (@opajaap) in the following topic of the Wordpress.org support:
https://wordpress.org/support/topic/cron-errors-3/

Hope it works for you too.

[jessuppi]

Thanks for sharing @unstatusthequo

I have seen this on some SlickStack sites and not others, immediately after setup is complete. I'm not sure but it's probably caused by one of our default MU plugins.

There are a few relevant threads on this issue:

https://wordpress.org/support/topic/wp-cron-php-problem/

Since I'm not sure what is causing it, I'm not sure what the fix would be yet, so we'll leave this Issue open for now and welcome new input on this. In any case, it is not a critical error.

[jessuppi]

Thanks very much for sharing that @EdTrojas and apologies for the long delay.

Here's a few other relevant threads now:

Ref: https://wordpress.org/support/topic/wp-cron-php-problem/
Ref: https://wordpress.org/support/topic/invalid-argument-supplied-for-foreach-157/
Ref: https://wordpress.org/support/topic/cron-errors-3/
Ref: https://wordpress.org/support/topic/warning-with-wp-cron/

Also this comment seems relevant, in regard to plugins causing this, although I'm not sure it's accurate for all cases:

@autotutorial
3 years, 1 month ago
Hello @lukeau, the problem is that $ crons is created with the first parameter as a boolean value. I’m sure the text won’t be investigative. This error, theme, plugin or core WordPress :/ obviously the cron is retrieved from the database, maybe that fake means not to run any cron? Currently I can’t answer. ...

TLDR I think this was probably caused by one of our MU plugins previously, some of which haven't been updated in a while and have some rather complex coding style that we will be abandoning in the future.

Since we have since removed several MU plugins from our default installation, and since this doesn't seem to be directly caused by SlickStack, I'm going to close this Issue for now.

If any further feedback on this feel free to comment here or on the repos of our various plugins --