如何通过附件名称/URL而非ID获取附件？

Got it, so you want to fetch WordPress attachments using their filename or a custom URL instead of the default numeric ID? Let's break down how to do this, including building on the code snippet you provided.

First: Understand Your Existing Code #

The code you shared modifies attachment links to point to your site's homepage with an attachment_id parameter—this lets you access attachments via ID through a unified URL format:

function wpa_attachment_link( $link, $id ){ 
    return home_url() . '/?attachment_id=' . $id; 
} 
add_filter( 'attachment_link', 'wpa_attachment_link', 10, 2 );

But to use names or custom URLs instead, we'll expand this functionality.

Step 1: Create User-Friendly Attachment URLs with Filenames #

First, let's adjust the attachment links to use the file's name (instead of ID) for cleaner, more readable URLs. Replace your existing filter with this:

function wpa_custom_attachment_link( $link, $id ) {
    $attachment = get_post( $id );
    $filename = basename( get_attached_file( $id ) );
    // Strip the file extension for a cleaner URL (optional)
    $slug = pathinfo( $filename, PATHINFO_FILENAME );
    return home_url( '/attachment/' . $slug );
}
add_filter( 'attachment_link', 'wpa_custom_attachment_link', 10, 2 );

Now your attachment links will look like yoursite.com/attachment/my-vacation-photo instead of the ID-based version.

Step 2: Make WordPress Recognize the Custom URL #

Next, we need to tell WordPress how to handle these new URLs and fetch the right attachment by filename. Add these functions to your theme's functions.php or a custom plugin:

// Add rewrite rule for our custom attachment URLs
function wpa_attachment_by_name_rewrite() {
    add_rewrite_rule(
        'attachment/([^/]+)/?$',
        'index.php?attachment_name=$matches[1]',
        'top'
    );
}
add_action( 'init', 'wpa_attachment_by_name_rewrite' );

// Register the custom query variable
function wpa_add_attachment_name_var( $vars ) {
    $vars[] = 'attachment_name';
    return $vars;
}
add_filter( 'query_vars', 'wpa_add_attachment_name_var' );

// Fetch the attachment when the custom URL is accessed
function wpa_load_attachment_by_name() {
    if ( get_query_var( 'attachment_name' ) ) {
        $filename_slug = get_query_var( 'attachment_name' );
        
        // Look for attachments matching the filename (without extension)
        $attachments = get_posts( array(
            'post_type' => 'attachment',
            'meta_query' => array(
                array(
                    'key' => '_wp_attached_file',
                    'value' => $filename_slug,
                    'compare' => 'LIKE'
                )
            ),
            'posts_per_page' => 1
        ) );
        
        if ( $attachments ) {
            // Redirect to the actual attachment file URL
            wp_redirect( wp_get_attachment_url( $attachments[0]->ID ) );
            exit;
        } else {
            // Trigger a 404 if no matching attachment is found
            global $wp_query;
            $wp_query->set_404();
            status_header( 404 );
        }
    }
}
add_action( 'template_redirect', 'wpa_load_attachment_by_name' );

Important: After adding this code, go to your WordPress admin > Settings > Permalinks and click "Save Changes" to flush the rewrite rules.

Step 3: Fetch Attachments by Filename Directly in Code #

If you need to grab an attachment by filename within your theme/plugin code (without using the URL), use this helper function:

function wpa_get_attachment_by_filename( $filename ) {
    $attachments = get_posts( array(
        'post_type' => 'attachment',
        'meta_query' => array(
            array(
                'key' => '_wp_attached_file',
                'value' => $filename,
                'compare' => 'LIKE'
            )
        ),
        'posts_per_page' => 1
    ) );
    
    return $attachments ? $attachments[0] : false;
}

// Usage example:
$my_attachment = wpa_get_attachment_by_filename( 'my-vacation-photo.jpg' );
if ( $my_attachment ) {
    $attachment_url = wp_get_attachment_url( $my_attachment->ID );
    // Do something with the URL here
}

内容的提问来源于stack exchange，提问作者Gaurav Kumeriya