At WP Front-end I create a upload form for users.

That form has three input fields (title, tags and upload).

So I want to add "Title - Tag - file_name" as alt attribute for images during the file upload.

How can I do with my code below?

if ($gui == 'upload') {
    if (!function_exists('wp_generate_attachment_metadata')){
        require_once(ABSPATH . "wp-admin" . '/includes/image.php');
        require_once(ABSPATH . "wp-admin" . '/includes/file.php');
        require_once(ABSPATH . "wp-admin" . '/includes/media.php');
    if ($_FILES) {
       foreach ($_FILES as $file => $array) {
           if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
              return "Upload Err: " . $_FILES[$file]['error'];
           $attach_id = media_handle_upload( $file, $newPost );
   if ($attach_id > 0){
       //and if you want to set that image as Post  then use:
  • 1
    First, better use admin_url(). Second, how exactly is the alt-HTML tag displayed? Does it come from caption, or something else? HInt: There's no alt-Tag in the meta data.
    – kaiser
    Jul 11, 2013 at 11:11
  • 3
    An alt attribute must be a meaningful, functional replacement for an image. File names are the opposite.
    – fuxia
    Jul 11, 2013 at 15:11

1 Answer 1


The alt text is stored in the postmeta database table by WordPress, therefore we have to update the postmeta of the given attachment. The reference is done via the unique attachment ID, and the meta_key we are targeting is the _wp_attachment_image_alt.

So, to set the alt text, we can do the following:

update_post_meta($attach_id, '_wp_attachment_image_alt', 'Your alt text');



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