For example, I would like to find out if the function
To answer the immediate question - yes, the manual once had it marked deprecated and that was removed. The problem was reported in bug #71367 and fixed in January this year, though apparently not in all translations.
Note that this was a "soft" deprecation, meaning that an
E_DEPRECATED runtime notice was not raised when the function was used - it was only mentioned in the manual.
To get a manual entry's history:
On each page underneath the "Change language" dropdown selector there is an "Edit" link:
Follow it to open PHP's online docbook editor, where you'll be greeted with a login prompt. Click Anonymous login and it'll load up the editor for that page.
On the bar separating the panels click the ≫ expander:
And in the panel that opens hit the reload button in the "Log" tab:
which'll let you read the changelog and perform diffs between revisions: