How to close unclosed HTML Tags?

Question

Whenever we are fetching some user inputed content with some editing from the database or similar sources, we might retrieve the portion which only contains the opening tag

Answer 1

You can use Tidy:

Tidy is a binding for the Tidy HTML clean and repair utility which allows you to not only clean and otherwise manipulate HTML documents, but also traverse the document tree.

or HTMLPurifier

HTML Purifier is a standards-compliant HTML filter library written in PHP. HTML Purifier will not only remove all malicious code (better known as XSS) with a thoroughly audited, secure yet permissive whitelist, it will also make sure your documents are standards compliant, something only achievable with a comprehensive knowledge of W3C's specifications.