Are there some rules/restrictions for seo friendly text?

Making my php app seo friendly are there some rules/restrictions for specific letters/symbols in
title, meta_description, meta_keywords meta tags?


You can forget about meta keywords, as Google ignores it, and I believe all the other large search engines do, too.

If you’re worrying about specific characters for SEO, you’re vastly over-thinking things. I suggest you read Google’s “Search Engine Optimization Starter Guide”, to learn what is and isn’t important.