Post Meta Boxes Quick start

quick-post-meta.php

<?php
add_action( 'load-post.php', 'spi_post_meta_boxes_setup' );
add_action( 'load-post-new.php', 'spi_post_meta_boxes_setup' );

function spi_post_meta_boxes_setup() {
	add_action( 'add_meta_boxes', 'spi_add_post_meta_boxes' );
    add_action( 'save_post', 'spi_save_post_meta', 10, 2 );
}

function spi_add_post_meta_boxes() {
	add_meta_box(
    'hdsl-gallery',      // Unique ID
    esc_html__( 'Add gallery', 'hdsl' ),    // Title
    'hdsl_gallery_meta_box',   // Callback function
    'wg_deal',         // Admin page (or post type)
    'side',         // Context
    'default'         // Priority
  );
	add_meta_box(
    'hdsl-top-det',      // Unique ID
    esc_html__( 'Add Image on Top', 'hdsl' ),    // Title
    'hdsl_top_img_meta_box',   // Callback function
    'wg_deal',         // Admin page (or post type)
    'side',         // Context
    'default'         // Priority
  );
}

function hdsl_gallery_meta_box($object, $box) {
	?>

  <?php wp_nonce_field( basename( __FILE__ ), 'hdsl_gallery_nonce' ); ?>

  <p>
  	<label for="hdsl-gallery"><?php _e( "Add ID's of images to the gallery.", 'hdsl' ); ?></label>
    <br />
    <?php 
    $field_value = get_post_meta( $object->ID, '_hdsl_gallery1', true );
    $args = array (
    	'wpautop' => false,
        'tinymce' => false,
        'quicktags' => false,
        'drag_drop_upload' => true,
        'textarea_rows' => 1
  	); 
   wp_editor( $field_value, '_hdsl_gallery1' , $args ); ?>
   </p>

<?php 
}

function hdsl_top_img_meta_box($object, $box) {
	?>

  <?php wp_nonce_field( basename( __FILE__ ), 'hdsl_top_img_nonce' ); ?>

  <p>
  	<label for="hdsl-top-img"><?php _e( "Add image to show up on top of deal details page.", 'hdsl' ); ?></label>
    <br />
    <?php 
    $field_value = get_post_meta( $object->ID, '_hdsl_top_img', true );
    $args = array (
    	'wpautop' => true,
        'tinymce' => false,
        'quicktags' => false,
        'drag_drop_upload' => true,
        'textarea_rows' => 1
  	); 
   wp_editor( $field_value, '_hdsl_top_img' , $args ); ?>
   </p>

<?php 
}

/* Save the meta box's post metadata. */
function spi_save_post_meta( $post_id, $post ) {

  /* Verify the nonce before proceeding. */
  if ( !isset( $_POST['hdsl_gallery_nonce'] ) || !wp_verify_nonce( $_POST['hdsl_gallery_nonce'], basename( __FILE__ ) ) )
    return $post_id;
  if ( !isset( $_POST['hdsl_top_img_nonce'] ) || !wp_verify_nonce( $_POST['hdsl_top_img_nonce'], basename( __FILE__ ) ) )
	return $post_id;

  /* Get the post type object. */
  $post_type = get_post_type_object( $post->post_type );

  /* Check if the current user has permission to edit the post. */
  if ( !current_user_can( $post_type->cap->edit_post, $post_id ) )
    return $post_id;

  $new_meta_value = ( isset( $_POST['_hdsl_gallery1'] ) ? $_POST['_hdsl_gallery1'] : '' );
  $new_meta_value1 = ( isset( $_POST['_hdsl_top_img'] ) ? $_POST['_hdsl_top_img'] : '' );

  /* Get the meta key. */
  $meta_key = '_hdsl_gallery1';
  $meta_key1 = '_hdsl_top_img';

  /* Get the meta value of the custom field key. */
  $meta_value = get_post_meta( $post_id, $meta_key, true );
  $meta_value1 = get_post_meta( $post_id, $meta_key1, true );

  /* If a new meta value was added and there was no previous value, add it. */
  if ( $new_meta_value && '' == $meta_value )
    add_post_meta( $post_id, $meta_key, $new_meta_value, true );

  /* If the new meta value does not match the old value, update it. */
  elseif ( $new_meta_value && $new_meta_value != $meta_value )
    update_post_meta( $post_id, $meta_key, $new_meta_value );

  /* If there is no new meta value but an old value exists, delete it. */
  elseif ( '' == $new_meta_value && $meta_value )
    delete_post_meta( $post_id, $meta_key, $meta_value );

  if ( $new_meta_value1 && '' == $meta_value1 )
    add_post_meta( $post_id, $meta_key1, $new_meta_value1, true );

  /* If the new meta value does not match the old value, update it. */
  elseif ( $new_meta_value1 && $new_meta_value1 != $meta_value1 )
    update_post_meta( $post_id, $meta_key1, $new_meta_value1 );

  /* If there is no new meta value but an old value exists, delete it. */
  elseif ( '' == $new_meta_value1 && $meta_value1 )
    delete_post_meta( $post_id, $meta_key1, $meta_value1 );
}