Problem with PHP "Scheduled Tasks"

I have a PHP script I need to run monthly.

I've set it up in "Scheduled Tasks", and when I test it from inside the configuration page (Run Now button) everything is ok, but when I save it (OK button) and try to run it from the Scheduled Task list (Run Now link), it miserably fails with the following diagnostic:


If instead of the PHP 5.6.23 I choose PHP 5.4.16 by OS vendor, then I get:


Problem with PHP "Scheduled Tasks"