A simple PHP script that allows users that allows WHMCS users to retrieve Product Bundle details including Display Price, Description, et al. Responses output is JSON encoded. Tested in WHMCS v6.3.

GetBundles.php

<?php

        // HTTP USAGE: 
        // http://example.com/GetBundles.php?bid=
        // BASH CLI EXAMPLE USAGE:
        // export QUERY_STRING="bid=2" ; php -e -r 'parse_str($_SERVER["QUERY_STRING"], $_GET); include "GetBundles.php";'

        $db_host = "mysql.databasehost.ext";
        $db_name = "mysqlDatabaseName";
        $db_user = "MysqlUsername";
        $db_pass = "MySq1p@Ssw0rd!";
        
        $BUNDLE = $_GET["bid"];

        $link = new PDO("mysql:host=$db_host;dbname=$db_name", $db_user, $db_pass);
        $link->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $link->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
        $link->quote($BUNDLE);
        $stmt = $link->prepare("SELECT * FROM tblbundles WHERE id = :bid");
        $stmt->bindParam(':bid', $BUNDLE, PDO::PARAM_STR);
        $stmt->execute();
        $dbRow = $stmt->fetchAll(PDO::FETCH_ASSOC);
        echo json_encode($dbRow, JSON_UNESCAPED_UNICODE);

?>