00-save-metadata.php

<?php

/**
 * Save the options in the meta box.
 *
 * @since    1.0.0
 *
 * @param    int    $post_id    The ID of the current post
 */
public function save( $post_id ) {

  // Note: Guard clauses removed for readability.
  // Assume $metadata is set earlier in this function.
  
  update_post_meta( $post_id, 'acme-custom-meta-data', $metadata );

}

01-inline-edit-save-metadata.php

<?php

/**
 * Save the options in the meta box. Ignore the action if it's coming from the
 * Bulk Edit screen.
 *
 * @since    1.0.0
 *
 * @param    int    $post_id    The ID of the current post
 */
public function save( $post_id ) {

  // Note: Guard clauses removed for readability.
  // Assume $metadata is set earlier in this function.
  
  if ( isset( $_POST['_inline_edit'] ) ) {
    return;
  }
  
  update_post_meta( $post_id, 'acme-custom-meta-data', $metadata );

}