Bitrix: the reason for the white screen when updating PHP?

Question

1C-Bitrix

There is a site on the 14th version of Bitrix. You need to update to a newer version. Now the server is running (Fast CGI) PHP 5.4 (it works correctly on this version), and version 5.6 is needed to gradually update Bitrix. When updating PHP, a white screen appears both when displaying pages and when trying to enter the admin panel. All basic recommendations in this case are immediately implemented: increase memory_limit, switch dbconn and settings configs to mysqli, enable all possible forms of logging/debugging in dbconn, settings, index.php files (adding ini_set('error_reporting', E_ALL) directive) and php.ini (obviously, there is nothing in the error logs and page output), disabling all modules in case one of them is buggy, clearing the cache. Nothing helped.

Answer 1

Before updating, in the admin panel in the settings of the main module, enable the output of errors and warnings.
In newer versions of Bitrix, you can enable debugging in the /bitrix/.settings.php file, but I don’t even remember if it was in the 14th version. If so, set the 'debug' => true parameter in the exception_handling block.
After that, look at the server error logs and figure out what exactly fell.

Answer 2

Look in the server's error_log , clear init.php for the time of debugging.
It is not required to update 5.6, you can immediately 7.
You can read about my update experience here .