How to add a protocol to URLs from WordPress post content

Sometimes you have URLs without http:// OR https:// into WordPress post content.

So you can use the following function for that. You can use this function for the_content filter for WP. And also you can use this anywhere in PHP code other than WP.

https://gist.github.com/BhargavBhandari90/67489aad26967f6afe2d6e52f278cc99