1. Compile PHP yourself (no)
2. Use an untrusted third party repo (probably not)
3. Upgrade OS to latest
4. (apparently) Use FreeBSD instead.
For all I know this could change. The current release schedule of PHP is greatly accelerated from what it was 5-10 years ago, and we're all still adjusting I think.
If you can't trust Ondřej Surý's repo, you're gonna be disappointed when you see who maintains the PHP packages in Debian's official repo.