Add Missing Alt Tags To WordPress Images

WordPress snippet to put into your functions.php file to search your content for images which don’t have an alt attribute. If they don’t have an alt attribute this function will add it in with a default of the post title.

function add_alt_tags($content)
{
        global $post;
        preg_match_all('/<img (.*?)/>/', $content, $images);
        if(!is_null($images))
        {
                foreach($images[1] as $index => $value)
                {
                        if(!preg_match('/alt=/', $value))
                        {
                                $new_img = str_replace('<img', '<img alt="'.$post->post_title.'"', $images[0][$index]);
                                $content = str_replace($images[0][$index], $new_img, $content);
                        }
                }
        }
        return $content;
}
add_filter('the_content', 'add_alt_tags', 99999);