$output = preg_replace('/<(((?!br)[^>])*)>\r*\n*\s*(<br\s?\/?>)*\r*\n*\s*<(((?!br)[^>])*)>/i', '<$1><$4>', $output);

A regular expression for removing <br> and <br> (case insensitive) between HTML elements if there is no content between the HTML elements.  It was written for fixing extra line spaces created in a WordPress visual editor after the content of the visual editor was returned from the PHP nl2br() method.

Remove superfluous line breaks between HTML elements.

regex, php, wordpress

PHP