Absolutely and evidence of this is always only a Google search away. Search on how to do something with a database and the results you get are riddled with things like SQL injection vulnerabilities, even when the source of the official documentation.
To follow on from this: Language Community Litmus Test: Database Placeholders. An informal survey shows PHP joint bottom, with all but one of the top 5 hits for "PHP database tutorial" promoting insecure methods.
And, as you mention, the official PHP tutorial had beginner-level security holes in it for YEARS. The whole community is riddled with this crap.