正则表达式以查找链接到图像的定位标记

Question

I'm using this code in my WordPress theme functions.php to add a "fancybox" class to linked images. However, I do not want to add the fancybox class to images that are linked to non-image URLs.

In other words: currently the script will add the "fancybox" class to an HTML structure like this (which I do not want):

<a href="http://acme.com/a-non-image-link"> <img src="http://acme.com/image.jpg" /> </a>

Where as I only want to add the class to structures like:

<a href="http://acme.com/an-image.jpg"> <img src="http://acme.com/an-image.jpg" /> </a>

or

<a href="http://acme.com/an-image.jpg"> <img src="http://acme.com/another-image.jpg" /> </a>

How can I modify the regex expression in this code to only include anchor tags whose HREF attribute contains .jpg , .jpeg , .png , or .gif ?

Thank you!

        // Add fancybox class to linked images
        function add_classes_to_linked_images($html) {
            $classes = 'fancybox fancybox-img'; // can do multiple classes, separate with space

            $patterns = array();
            $replacements = array();

            $patterns[0] = '/<a(?![^>]*class)([^>]*)>\s*<img([^>]*)>\s*<\/a>/'; // matches img tag wrapped in anchor tag where anchor tag where anchor has no existing classes
            $replacements[0] = '<a\1 class="' . $classes . '"><img\2><span class="post-content-fb-btn"></span></a>';

            $patterns[1] = '/<a([^>]*)class="([^"]*)"([^>]*)>\s*<img([^>]*)>\s*<\/a>/'; // matches img tag wrapped in anchor tag where anchor has existing classes contained in double quotes
            $replacements[1] = '<a\1class="' . $classes . ' \2"\3><img\4> <span class="post-content-fb-btn"></span></a>';

            $patterns[2] = '/<a([^>]*)class=\'([^\']*)\'([^>]*)>\s*<img([^>]*)>\s*<\/a>/'; // matches img tag wrapped in anchor tag where anchor has existing classes contained in single quotes
            $replacements[2] = '<a\1class="' . $classes . ' \2"\3><img\4> <span class="post-content-fb-btn"></span></a>';

            $html = preg_replace($patterns, $replacements, $html);

            return $html;
        }

        add_filter('the_content', 'add_classes_to_linked_images', 100, 1);

Answer 1

The following should work with one caveat. The link needs to be on a separate line to the image tag, or the file extension of the image will create a match.

/<a(.*?)href=('|\")(.*?).(bmp|gif|jpeg|jpg|png)('|\")(.*?)>/i

Maybe someone can improve on it rather than posting sarcastic comments :)