If, instead of an array, you pass an object PHP will automatically cast the object as an array so you can use it directly in vprintf.
<?php
$object = new stdClass();
$object->Property1 = 'Value 1';
$object->Property2 = 'Value 2';
vprintf('%-20s %-20s', $object);
/* will output
Value 1 Value 2
*/
?>