catch fatal error information in older php

catch fatal error information in older php

We have an old php instance running on a server. php 5.1.6 precisely. But
it is handling all payments and some other critical stuff so there is no
plan of upgrading it as of now. There are a couple of crons running. The
requirement is to catch fatal errors. However as we know, function
error_get_last which does the job of gathering error information, was not
available in that version of php.
I have scoured the web for any method of catching the fatal error, but
have not succeeded yet. There is a way to do that mentioned by someone
here http://php.net/manual/en/function.error-get-last.php, however that
did not work. Please help.