tjsix

It’s probably because the $key is not defined.. define the key at the top, you can set it to whatever you want and it’s usually the shortname for the theme.. so just set it to $key = mytheme; or whatever.. the key just needs to be a unique identifier..

Also, in the create_meta_box and display_meta_box functions call the key in the global scope with global $key;

I’m a little confused on what you’re asking, you want to add meta boxes to all of your pages/post types or just your custom ones? if you want custom fields that don’t neccesarily appear under the custom fields tab just do something like this:

//Put all your arguments and details in the array.. Example:
$meta_boxes = array(
       "background_image" => array(
		"name" => "background_image",
		"title" => "Page Background Image",
		"type" => "text",
		"description" => "A background image for the page.")
);
//Hook into the admin_menu
add_action('admin_menu', 'create_meta_box');
function create_meta_box() {
	add_meta_box( 'meta-box-id', 'The Title', 'display_meta_box', 'post', 'normal', 'high' );
}

//Display the meta_boxes
function display_meta_box($meta_boxes) {
$data = get_post_meta($post->ID, $key, true);
<div class="form_wrap">
<?php foreach($meta_boxes as $meta_box) {
<div class="form_field">
<label for="<?php echo $meta_box['name']; ?>"><?php echo $meta_box['title']; ?></label>
<input type="text" name="<?php echo $meta_box['name']; ?>" value="<?php echo htmlspecialchars( $data[$meta_box['name']] ); ?>" />
<p><?php echo $meta_box[ 'description' ]; ?></p>
</div>
</div>
  }
}

//Function to save your fields
add_action('save_post', 'save_meta_box');
function save_meta_box( $post_id ) {
  global $post;
    foreach( $meta_boxes as $meta_box ) {
		$data[ $meta_box[ 'name' ] ] = $_POST[ $meta_box[ 'name' ] ];
	}
  //Make sure the POST info came from WP..
   if ( !wp_verify_nonce( $_POST[ $key . '_wpnonce' ], plugin_basename(__FILE__) ) )
	return $post_id;

	if ( !current_user_can( 'edit_post', $post_id ))
	return $post_id;

	update_post_meta( $post_id, $key, $data );
    }
}

Obviously this can be expanded upon to display the form however you’d like but thats the gist of what needs to be done for any custom meta box info you want to add..