Any php file with the following lines in it give me an error:
<?php foreach ($config->rsExtra as $field) { ?>

The error is => warning: invalid argument supplied for foreach() .....

This suddenly showed up, even in the administrator side of the website?

Any idea how this can be. We didn't change the site for more than 4 weeks and now this error shows up.

I deleted all those lines with code to display the extra customer fields for now.

We use Artio booking 1.4.3 in Joomla 2.5.7

Hello,

This is really old version and problem could be already solved in actual version.
But there is problem that actual version 1.6.1 is not compatible with Joomla 2.5. We offer free modification for customers what use Joomla 2.5 and have Book it! 1. Their orders are modified to Book it! 2, but I do not see any actual order with Book it! 1 in your account.

So, that warning is problematic only in that way that it is displayed to customers and it doesn't look well. You can hide it by changing settings in Global Configuration -> tab Server -> option Error Reporting -> set to None
Error reporting will be visible only in logs and it will no more annoy your customers.

Functionality will be not broken, because $config->rsExtra is not set. Code will automatically continue after foreach cycle. It only reports warning, because code don't know if it is error or not, but it will not break component functionality.

Correct, in my account I don't have a booking1, only a 2. But I am also admin of a site where I did not buy the booking module. i will leave it like this for now, as long as we are not using the extra fields.

Thanks for your reply, Ronald :)