WordPress : Add Meta Boxes

gistfile1

// Add Meta Boxes
$key = "portfolio"; // POST TYPE NAME
$meta_boxes = array(
	"caption" => array(
		"name" => "caption", // "name" attribute for input element
		"title" => "Portfolio Item Caption", // "lable" of the field
		"description" => "Description for this field" // helpful description shown in WordPress Admin Panel
	),
	"gallery" => array(
		"name" => "gallery-id",
		"title" => "Gallery ID",
		"description" => "Description for this field"
	)
);
 
 /**************************************
 * NO NEED TO EDIT ANYTHING BELOW THIS *
 ***************************************/
function wpb_create_meta_box() {
	global $key;
	if( function_exists( 'add_meta_box' ) ) {
	add_meta_box( 'new-meta-boxes', ucfirst( $key ) . ' Options', 'display_meta_box', $key, 'normal', 'high' );
	}
}
 
function display_meta_box() {
	global $post, $meta_boxes, $key;
?>
	<div class="form-wrap">
		<?php
		wp_nonce_field( plugin_basename( __FILE__ ), $key . '_wpnonce', false, true );
		foreach($meta_boxes as $meta_box) {
		$data = get_post_meta($post->ID, $key, true);
		?>
		<div class="form-field form-required">
		<label for="<?php echo $meta_box[ 'name' ]; ?>"><?php echo $meta_box[ 'title' ]; ?></label>
		<textarea name="<?php echo $meta_box[ 'name' ]; ?>"><?php echo htmlspecialchars( $data[ $meta_box[ 'name' ] ] ); ?></textarea>
		<p><?php echo $meta_box[ 'description' ]; ?></p>
		</div>
		<?php } ?>
	</div>
<?php
}
 
function wpb_save_meta_box( $post_id ) {
	global $post, $meta_boxes, $key;
	foreach( $meta_boxes as $meta_box ) {
	$data[ $meta_box[ 'name' ] ] = $_POST[ $meta_box[ 'name' ] ];
	}
	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 );
}
 
add_action( 'admin_menu', 'wpb_create_meta_box' );
add_action( 'save_post', 'wpb_save_meta_box' );