function postorder($tree)
{
$lst = array();
if (!$tree) {
return $lst;
}
$stack = new SplStack();
$stack->push($tree);
$stack->rewind();
$prev = null;
while ($stack->valid()) {
$curr = $stack->current();
// go down the tree.
//check if current node is leaf, if so, process it and pop stack,
//otherwise, keep going down
if (!$prev || @$prev->left->key == @$curr->key || @$prev->right->key == @$curr->key) {
//prev == null is the situation for the root node
if ($curr->left) {
$stack->push($curr->left);
$stack->rewind();
} else {
if ($curr->right) {
$stack->push($curr->right);
$stack->rewind();
} else {
$stack->pop();
$stack->rewind();
$lst[] = $curr->key;
}
}
//go up the tree from left node
//need to check if there is a right child
//if yes, push it to stack
//otherwise, process parent and pop stack
} else {
if (@$curr->left->key == @$prev->key) {
if (@$curr->right->key) {
$stack->push($curr->right);
$stack->rewind();
} else {
$stack->pop();
$stack->rewind();
$lst[] = $curr->key;
}
} else {
if (@$curr->right->key == @$prev->key) {
$stack->pop();
$stack->rewind();
$lst[] = $curr->key;
}
}
}
$prev = $curr;
}
return $lst;
}
/**
* Logs with an arbitrary level.
*
* @param string $level
* @param string|array $message a textual message, encoded JSON or array to encode into JSON
* @param array $context context regarding the message, if this is included it will
* added to the message as json or included in the json payload
* @throws \InvalidArgumentException
* @return null
*/
public function log($level, $message, array $context = array())
{
$this->connectIfNotConnected();
if (is_array($message)) {
$message = json_encode($message);
}
if (!is_string($message)) {
throw new \InvalidArgumentException('the message argument needs to be a string or an array');
} else {
$isJson = $this->isJSON($message);
if ($isJson) {
$json = json_decode($message, true);
if ("" != $this->_hostname) {
$json["hostname"] = $this->_hostname;
}
$json["level"] = $level;
if (count($context) > 0) {
$json["context"] = $context;
}
$message = json_encode($json);
} else {
$message = strtoupper($level) . " - " . $message;
if ("" != $this->_hostname) {
$message = "hostname={$this->_hostname} - " . $message;
if (count($context) > 0) {
$message .= " - " . json_encode($context);
}
}
}
$this->_writer_stack->rewind();
while ($this->_writer_stack->valid()) {
/** @var LogEntriesWriter $writer */
$writer = $this->_writer_stack->current();
$message = $writer->log($message, $isJson);
$this->_writer_stack->next();
}
$this->writeToSocket($this->substituteNewline($message) . PHP_EOL);
}
}
/**
* @return ResourceInterface
*/
public function current()
{
$resource = parent::current();
return $resource ? $this->transform($resource) : $resource;
}
