ACF preview update

functions.php

<?php
add_filter( 'get_post_metadata', 'get_preview_post_meta_data', 10, 4 );
add_action( 'wp_insert_post', 'save_preview_post' );
add_action( 'save_preview_postmeta', 'acf_save_preview_postmeta' );

function get_preview_post_meta_data( $meta_value, $post_id, $meta_key, $single ) {
  global $post;

  if ( ! empty( $_GET['preview'] ) && $post->ID == $post_id ) {
    $preview = wp_get_post_autosave( $post_id );

    if ( $preview ) {
      if ( $post_id != $preview->ID ) {
        $meta_value = get_post_meta( $preview->ID, $meta_key, $single );
      }
    }
  }

  return $meta_value;
}

/**
 * プレビュー時にメタデータも保存するためのフックを実行する
 *
 * @param $post_id
 */
function save_preview_post( $post_id ) {
  if ( wp_is_post_revision( $post_id ) ) {
    do_action( 'save_preview_postmeta', $post_id );
  }
}

/**
 * プレビュー時にACFのメタデータも保存する
 *
 * @param $post_id
 */
function acf_save_preview_postmeta( $post_id ) {
  if ( ! function_exists( 'get_field_object' ) ) {
    return;
  }

  if ( isset( $_POST['acf'] ) && is_array( $_POST['acf'] ) ) {
    foreach ( $_POST['acf'] as $key => $value ) {
      $field = get_field_object( $key );

      if ( empty( $field['name'] ) || empty( $field['key'] ) ) {
        continue;
      }

      update_metadata( 'post', $post_id, $field['name'], $value );
      update_metadata( 'post', $post_id, "_" . $field['name'], $field['key'] );
    }
  }
}