[WordPress] [SEO] obfuscate links by adding a class to any <a> element

<?php

/**************************************************************************************\
|* Links obfuscation - add class "obfuscate" to any <a> element to obfuscate its link *|
\**************************************************************************************/

// Add this code to your child theme's functions.php file, then just add the class "obfuscate" to any <a> element to obfuscate its link by replacing it with a <span> element with no readable link.
// The obfuscated elements inherits the original <a> element's classes, along with a "akn-obf-link" class, so you might need to add CSS to style the "akn-obf-link" class so that it looks like a link to the visitor, maybe at least to add a cursor:pointer.
// On right click, the obfuscated link will be wrapped with a proper <a> element with the "akn-deobf-link" for a brief moment, so that a proper context menu appears, you can remove that behaviour by setting the "deobfuscate_on_right_click" option to false in the code bellow.

// Edit 2022-04-05 - modified regex to allow for html elements and new lines into the <a> element, modified callback so the obfuscated element inherits the original link's classes, modified JS to add mousewheel click and right click options.

// Edit 2023-01-26 - greatly improved regex thanks to @MadMaxInfinity on Stack Overflow, it now both allows more matches in different scenarios and returns less false positives matches, more infos on his answer here: https://stackoverflow.com/a/75234749/2498324

// Edit 2023-02-08 - improved class regex thanks to @MadMaxInfinity on Stack Overflow again.

add_action('wp_loaded', 'buffer_start');
function buffer_start() {
    ob_start('akn_ofbuscate_buffer');
}
add_action('shutdown', 'buffer_end');
function buffer_end() {
    ob_end_flush();
}
function akn_ofbuscate_buffer($buffer) {
    $result = preg_replace_callback('#<a[^>]+((?<=\s)href=(\"|\')([^\"\']*)(\'|\")[^>]+(?<=\s)class=(\"|\')[^\'\"]*(?<!\w|-)obfuscate(?!\w|-)[^\'\"]*(\"|\')|(?<=\s)class=(\"|\')[^\'\"]*(?<!\w|-)obfuscate(?!\w|-)[^\'\"]*(\"|\')[^>]+(?<=\s)href=(\"|\')([^\"\']*)(\'|\"))[^>]*>(.*)<\/a>#miUs', function($matches) {
        preg_match('#<a[^>]+(?<=\s)class=[\"|\\\']([^\\\'\"]+)[\"|\\\']#imUs',$matches[0],$matches_classes);
        $classes = trim(preg_replace('/\s+/',' ',str_replace('obfuscate','',$matches_classes[1])));
        return '<span class="akn-obf-link'.($classes?' '.$classes:'').'" data-o="'.base64_encode($matches[3]?:$matches[10]).'" data-b="'.((strpos(strtolower($matches[0]),'_blank')!==false)?'1':'0').'">'.$matches[12].'</span>';
    }, $buffer);
    return $result;
}
add_action('wp_footer', 'akn_ofbuscate_footer_js');
function akn_ofbuscate_footer_js() {
    ?>
        <script>
            jQuery(document).ready(function($) {
                // options you can change
                var deobfuscate_on_right_click = true;
                // function to open link on click
                function akn_ofbuscate_clicked($el,force_blank) {
                    if (typeof(force_blank)=='undefined')
                        var force_blank = false;
                    var link = atob($el.data('o'));
                    var _blank = $el.data('b');
                    if (_blank || force_blank)
                        window.open(link);
                    else
                        location.href = link;
                }
                // trigger link opening on click
                $(document).on('click','.akn-obf-link',function() {
                    var $el = $(this);
                    if (!$el.closest('.akn-deobf-link').length)
                        akn_ofbuscate_clicked($el);
                });
                // trigger link openin in new tab on mousewheel click
                $(document).on('mousedown','.akn-obf-link',function(e) {
                    if (e.which==2) {
                        var $el = $(this);
                        if (!$el.closest('.akn-deobf-link').length) {
                            akn_ofbuscate_clicked($el,true);
                            return true;
                        }
                    }
                });
                // deobfuscate link on right click so the context menu is a legit menu with link options
                $(document).on('contextmenu','.akn-obf-link',function(e) {
                    if (deobfuscate_on_right_click) {
                        var $el = $(this);
                        if (!$el.closest('.akn-deobf-link').length) {
                            e.stopPropagation();
                            var link = atob($el.data('o'));
                            var _blank = $el.data('b');
                            $el.wrap('<a class="akn-deobf-link" href="'+link+'"'+(_blank?' target="_BLANK"':'')+'></a>').parent().trigger('contextmenu');
                            setTimeout(function() {
                                $el.unwrap();
                            },10);
                        }
                    }
                });
            });
        </script>
    <?php
}