Notify user for post status change

<?php function notify_post_status( $post_id = NULL, $user = '' ) {
	if ( ! isset($_POST["post_id"]) ) {
		$post_id = $_POST["post_id"];
	}
	else {
		return $post_id;
	}
	$post = get_post($post_id);
	$status = $post->post_status;
	$type = $post->post_type;
	$author_id = intval($post->post_author);
	$user = get_userdata( $author_id ); 
	
	//ignore admin
	if( $author_id == 1 ) return;
	
	// Which statuses should we send email for ?
	$send_statuses = array("publish","draft");
	// Send mails only for published (approved) || draft (rejected)
	if( ! in_array($status,$send_statuses)) return;
	// Only send for a specific custom post type ?
	//if( $type != "my_custom_post_type" ) return $post_id;

	$title = $post->post_title;
	$content  = $post->post_content;
    $blogname = get_bloginfo( 'name' );
  //  $to_admin = get_bloginfo( 'admin_email' );
    $to = $user->user_email;
	$frommail = 'noreply@my_domain.com';
    $permalink = get_permalink( $post_id );

    $headers = sprintf( "From: %s <%s>\r\n", $blogname, $frommail );
	$subject = sprintf( __( 'Your post status : %s','my_textdomain' ), $status );
	$msg = sprintf( __( 'Your post titled: %s ','my_textdomain' ), $title ) . "\r\n";
	$msg .= sprintf( __( 'status has been changed to : %s','my_textdomain' ), $title ) . "\r\n";
	
	if($status == "publish" ) {
		$msg .= sprintf( __( 'You can view it here : %s' ), $permalink ) . "\r\n";
	}

	// Save sent email for each status so it doesnt send email every time
	$sent_mails = get_post_meta($post_id,'post_notif_sent_mails',true);
	
	if($sent_mails) {
		// have sent mail for this status ?
		if ( in_array($status,$sent_mails) ) {
			return;
		}
		else {
			$sent_mails[] = $status;
		}
	}
	else {
		// no mail has been sent for this status, crate array, insert stat
		$sent_mails = array($status);
	}
	// send the mail, update the metadata
	update_post_meta($post_id,"post_notif_sent_mails",$sent_mails);
	wp_mail( $to, $subject, $msg, $headers );
}

?>