此解决方案将添加data-fancybox="group" 到默认生成的库链接[gallery] 短代码。无论主题是否HTML5 theme support 是否为库启用。

该解决方案通过使用post_gallery 筛选以访问库快捷码的输出。然后，使用PHP的DOMDocument() 和DOMXpath().

add_filter( \'post_gallery\', \'wpse_gallery_shortcode\', 10, 3 );
/**
 * Filters the default gallery shortcode output.
 *
 * @see gallery_shortcode()
 *
 * @param string $output   The gallery output. Default empty.
 * @param array  $attr     Attributes of the gallery shortcode.
 * @param int    $instance Unique numeric ID of this gallery shortcode instance.
 */
function wpse_gallery_shortcode( $output, $attr, $instance ) {
    // Temporarily remove our filter to prevent infinite loop.
    remove_filter( \'post_gallery\', \'wpse_gallery_shortcode\', 10, 3 );

    // Use WordPress\' native function for generating gallery output.
    $gallery_html = gallery_shortcode( $attr );

    // Create an instance of DOMDocument.
    $dom = new \\DOMDocument();

    // Supress errors due to malformed HTML.
    // See http://stackoverflow.com/a/17559716/3059883
    $libxml_previous_state = libxml_use_internal_errors( true );

    // Populate $dom with $gallery_html, making sure to handle UTF-8, otherwise
    // problems will occur with UTF-8 characters.
    // Also, make sure that the doctype and HTML tags are not added to our HTML fragment. http://stackoverflow.com/a/22490902/3059883
    $dom->loadHTML( mb_convert_encoding( $gallery_html, \'HTML-ENTITIES\', \'UTF-8\' ), LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD );

    // Restore previous state of libxml_use_internal_errors() now that we\'re done.
    // Again, see http://stackoverflow.com/a/17559716/3059883
    libxml_use_internal_errors( $libxml_previous_state );

    // Create an instance of DOMXpath.
    $xpath = new \\DOMXpath( $dom );

    // Match elements with the class gallery-icon (these can be <div> or <dt> depending on whether the theme has support for HTML5.
    // See http://stackoverflow.com/a/26126336/3059883
    $gallery_icons = $xpath->query( "//*[contains(concat(\' \', normalize-space(@class), \' \'), \' gallery-icon \')]" );

    // Iterate over the the gallery icons.
    foreach ( $gallery_icons as $gallery_icon ) {
        // Find the <a> tags and add our custom attribute and value.
        $gallery_icon_child_node_link = $xpath->query( "//a", $gallery_icon );
        foreach ( $gallery_icon_child_node_link as $node_link ) {
            $gallery_icon_data_fancy_box = $dom->createAttribute( \'data-fancybox\' );
            $gallery_icon_data_fancy_box->value = \'group\';

            $node_link->appendChild( $gallery_icon_data_fancy_box );                
        }
    }

    // Save the updated HTML.
    $gallery_html = $dom->saveHTML();   

    // Add our filter back so that it will run the next time that the gallery shortcode is used.
    add_filter( \'post_gallery\', \'wpse_gallery_shortcode\', 10, 3 );

    // Return the modified HTML.
    return $gallery_html;
}

您还可以考虑对这些类似问题的答案进行调整：

• Change the output for [gallery] shortcode

• add_filter and changing output captions of image gallery