Duplicate Post/Page Link

Duplicate posts, pages or any post type with 1-click by adding a duplicate link in the admin list of actions.

<?php
// Add duplicate button to post/page list of actions.
add_filter( 'post_row_actions', 'wpcode_snippet_duplicate_post_link', 10, 2 );
add_filter( 'page_row_actions', 'wpcode_snippet_duplicate_post_link', 10, 2 );
// Let's make sure the function doesn't already exist.
if ( ! function_exists( 'wpcode_snippet_duplicate_post_link' ) ) {
 /**
  * @param array   $actions The actions added as links to the admin.
  * @param WP_Post $post The post object.
  *
  * @return array
  */
 function wpcode_snippet_duplicate_post_link( $actions, $post ) {
  // Don't add action if the current user can't create posts of this post type.
  $post_type_object = get_post_type_object( $post->post_type );
  if ( null === $post_type_object || ! current_user_can( $post_type_object->cap->create_posts ) ) {
   return $actions;
  }
  $url = wp_nonce_url(
   add_query_arg(
    array(
     'action'  => 'wpcode_snippet_duplicate_post',
     'post_id' => $post->ID,
    ),
    'admin.php'
   ),
   'wpcode_duplicate_post_' . $post->ID,
   'wpcode_duplicate_nonce'
  );
  $actions['wpcode_duplicate'] = '<a href="' . $url . '" title="Duplicate item" rel="permalink">Duplicate</a>';
  return $actions;
 }
}
/**
 * Handle the custom action when clicking the button we added above.
 */
add_action( 'admin_action_wpcode_snippet_duplicate_post', function () {
 if ( empty( $_GET['post_id'] ) ) {
  wp_die( 'No post id set for the duplicate action.' );
 }
 $post_id = absint( $_GET['post_id'] );
 // Check the nonce specific to the post we are duplicating.
 if ( ! isset( $_GET['wpcode_duplicate_nonce'] ) || ! wp_verify_nonce( $_GET['wpcode_duplicate_nonce'], 'wpcode_duplicate_post_' . $post_id ) ) {
  // Display a message if the nonce is invalid, may it expired.
  wp_die( 'The link you followed has expired, please try again.' );
 }
 // Load the post we want to duplicate.
 $post = get_post( $post_id );
 // Create a new post data array from the post loaded.
 if ( $post ) {
  $current_user = wp_get_current_user();
  $new_post     = array(
   'comment_status' => $post->comment_status,
   'menu_order'     => $post->menu_order,
   'ping_status'    => $post->ping_status,
   'post_author'    => $current_user->ID,
   'post_content'   => $post->post_content,
   'post_excerpt'   => $post->post_excerpt,
   'post_name'      => $post->post_name,
   'post_parent'    => $post->post_parent,
   'post_password'  => $post->post_password,
   'post_status'    => 'draft',
   'post_title'     => $post->post_title . ' (copy)',// Add "(copy)" to the title.
   'post_type'      => $post->post_type,
   'to_ping'        => $post->to_ping,
  );
  // Create the new post
  $duplicate_id = wp_insert_post( $new_post );
  // Copy the taxonomy terms.
  $taxonomies = get_object_taxonomies( get_post_type( $post ) );
  if ( $taxonomies ) {
   foreach ( $taxonomies as $taxonomy ) {
    $post_terms = wp_get_object_terms( $post_id, $taxonomy, array( 'fields' => 'slugs' ) );
    wp_set_object_terms( $duplicate_id, $post_terms, $taxonomy );
   }
  }
  // Copy all the custom fields.
  $post_meta = get_post_meta( $post_id );
  if ( $post_meta ) {
   foreach ( $post_meta as $meta_key => $meta_values ) {
    if ( '_wp_old_slug' === $meta_key ) { // skip old slug.
     continue;
    }
    foreach ( $meta_values as $meta_value ) {
     add_post_meta( $duplicate_id, $meta_key, maybe_unserialize( $meta_value ) );
    }
   }
  }
  // Redirect to edit the new post.
  wp_safe_redirect(
   add_query_arg(
    array(
     'action' => 'edit',
     'post'   => $duplicate_id
    ),
    admin_url( 'post.php' )
   )
  );
  exit;
 } else {
  wp_die( 'Error loading post for duplication, please try again.' );
 }
} );