function media_upload_form_handler() {
  check_admin_referer( 'media-form' );

  $errors = null;

  if ( isset( $_POST['send'] ) ) {
    $keys    = array_keys( $_POST['send'] );
    $send_id = (int) reset( $keys );
  }

  if ( ! empty( $_POST['attachments'] ) ) {
    foreach ( $_POST['attachments'] as $attachment_id => $attachment ) {
      $post  = get_post( $attachment_id, ARRAY_A );
      $_post = $post;

      if ( ! current_user_can( 'edit_post', $attachment_id ) ) {
        continue;
      }

      if ( isset( $attachment['post_content'] ) ) {
        $post['post_content'] = $attachment['post_content'];
      }

      if ( isset( $attachment['post_title'] ) ) {
        $post['post_title'] = $attachment['post_title'];
      }

      if ( isset( $attachment['post_excerpt'] ) ) {
        $post['post_excerpt'] = $attachment['post_excerpt'];
      }

      if ( isset( $attachment['menu_order'] ) ) {
        $post['menu_order'] = $attachment['menu_order'];
      }

      if ( isset( $send_id ) && $attachment_id == $send_id ) {
        if ( isset( $attachment['post_parent'] ) ) {
          $post['post_parent'] = $attachment['post_parent'];
        }
      }

      
/**
 * Filters the attachment fields to be saved.
 *
 * @since 2.5.0
 *
 * @see wp_get_attachment_metadata()
 *
 * @param array $post       An array of post data.
 * @param array $attachment An array of attachment metadata.
 */
      $post = apply_filters( 'attachment_fields_to_save', $post, $attachment );

      if ( isset( $attachment['image_alt'] ) ) {
        $image_alt = wp_unslash( $attachment['image_alt'] );

        if ( get_post_meta( $attachment_id, '_wp_attachment_image_alt', true ) !== $image_alt ) {
          $image_alt = wp_strip_all_tags( $image_alt, true );

          // update_post_meta() expects slashed.
          update_post_meta( $attachment_id, '_wp_attachment_image_alt', wp_slash( $image_alt ) );
        }
      }

      if ( isset( $post['errors'] ) ) {
        $errors[ $attachment_id ] = $post['errors'];
        unset( $post['errors'] );
      }

      if ( $post != $_post ) {
        wp_update_post( $post );
      }

      foreach ( get_attachment_taxonomies( $post ) as $t ) {
        if ( isset( $attachment[ $t ] ) ) {
          wp_set_object_terms( $attachment_id, array_map( 'trim', preg_split( '/,+/', $attachment[ $t ] ) ), $t, false );
        }
      }
    }
  }

  if ( isset( $_POST['insert-gallery'] ) || isset( $_POST['update-gallery'] ) ) {
    ?>
		<script type="text/javascript">
		var win = window.dialogArguments || opener || parent || top;
		win.tb_remove();
		</script>
		<?php

    exit;
  }

  if ( isset( $send_id ) ) {
    $attachment = wp_unslash( $_POST['attachments'][ $send_id ] );
    $html       = isset( $attachment['post_title'] ) ? $attachment['post_title'] : '';

    if ( ! empty( $attachment['url'] ) ) {
      $rel = '';

      if ( str_contains( $attachment['url'], 'attachment_id' ) || get_attachment_link( $send_id ) === $attachment['url'] ) {