- print_r: documentation ( source)
<?php
$node = new stdClass();
$node->field_test = array('und' => array(0 => array('value' => 'test')));
$clone = clone $node;
$clone->field_test['und'] = array(0 => array('value' => 'modified'));
print_r($node->field_test);
print_r($clone->field_test);