add class to internal links in content

i want to add a class to all links inside of the_content, that point to other interal content, f.ex. other posts and pages. i want to do this automatically. dunno if the best practise would be, to look for content or try to hook into the tinymce editor.. and eather way around, i don’t know how..

How to Use Checkbox in Custom Option Page Using The Setting API

Can you please let me know how I can add a checkbox to Setting API in creating Custom Options Page? I am using the following code to add a txt box which is working perfectly but I am totally confused how to add chechbox to the setting API and options. I just tried ti update the input type to checkbox but I am not sure what to put in Value besides when I save the form the check box still appears unchecked!

How to Change Loop to Order Posts by Views (using wp-postviews plugin)

I hope somebody would be kind enough to help. I currently have a page that orders all of the posts by comment count, but I want to change the loop to order the posts by view count. I have installed the ‘wp-postviews.1.50’ plugin and have got it to display the number of views on each post, so I know that side of it is working, now I just need the loop code changed to order by most views, is this possible?

How to extend Media Library (WP 4.4)

I am trying to implement a new tab next to Media Library. I couldn’t find solution to implement this. I found an example how to implement a new tab in this link: https://gist.github.com/Fab1en/4586865 However the tab doesn’t show up in the modal form triggered by Add Media button. But if I call the media popup for Featured Image or any other custom button the “New Tab” I created shows up. I am really lost here, not sure why those tabs show up in one place and don’t in another.