PHP Flatten Array with multiple leaf nodes - php

Question

What is the best way to flatten an array with multiple leaf nodes so that each full path to leaf is a distinct return?
array("Object"=>array("Properties"=>array(1, 2)));
to yield
Object.Properties.1
Object.Properties.2
I'm able to flatten to Object.Properties.1 but 2 does not get processed with recursive function:
function flattenArray($prefix, $array)
{
$result = array();
foreach ($array as $key => $value)
{
if (is_array($value))
$result = array_merge($result, flattenArray($prefix . $key . '.', $value));
else
$result[$prefix . $key] = $value;
}
return $result;
}
I presume top down will not work when anticipating multiple leaf nodes, so either need some type of bottom up processing or a way to copy array for each leaf and process (althought that seems completely inefficient)

Answer 1

function flatten(array $data, $separator = '.') {
$result = array();
$stack = array();
$path = null;
reset($data);
while (!empty($data)) {
$key = key($data);
$element = $data[$key];
unset($data[$key]);
if (is_array($element)) {
if (!empty($data)) {
$stack[] = array($data, $path);
}
$data = $element;
$path .= $key . $separator;
} else {
$result[$path . $key] = $element;
}
if (empty($data) && !empty($stack)) {
list($data, $path) = array_pop($stack);
}
}
return $result;
}
var_dump(flatten(array("Object"=>array("Properties"=>array(1, 2)))));
Output:
array(2) {
["Object.Properties.0"]=>
int(1)
["Object.Properties.1"]=>
int(2)
}

Answer 2

Use function flatMapAssoc() from Kdyby Framework:
$flattened= array();
flatMapAssoc($array, function ($value, $keys) use (&$flattened) {
$flattened[implode('.', $keys)] = $value;
});
/**
* #param array|\Traversable $array
* #param callable $callback
* #return array
*/
function flatMapAssoc($array, $callback)
{
$callback = callback($callback);
$result = array();
$walker = function ($array, $keys = array()) use (&$walker, &$result, $callback) {
foreach ($array as $key => $value) {
$currentKeys = $keys + array(count($keys) => $key);
if (is_array($value)) {
$walker($value, $currentKeys);
continue;
}
$result[] = $callback($value, $currentKeys);
}
return $result;
};
return $walker($array);
}

Answer 3

I would use a wrapper function to hide implementation details (the prefix parameter)
and added an if branch to test for empty arrays. At last, in case of simple leaf you should use the $value variable and not the $key one.
$x = array("Object"=>array("Properties"=>array(1, 2), "test"=>array(), "post"));
function flatten ($array) {
return flattenArray('',$array);
}
function flattenArray($prefix, $array) {
$result = array();
foreach ($array as $key => $value) {
if (is_array($value)) {
if(count($value)) {
$result = array_merge($result, flattenArray($prefix."$key.", $value));
} else {
$result[] = "$prefix$key";
}
} else {
$result[] = "$prefix$value";
}
}
return $result;
}
echo join("\n", flatten($x));
If you want to mimic a tree structure, maybe you can use a different array structure. Something like this:
$y = array ("Object",
array("Properties", 1, 2),
"test",
"post"
);
and flattenArray becomes:
function flattenArray($prefix, $array) {
$result = array();
$prefix .=array_shift($array).'.';
foreach ($array as $value) {
if (is_array($value)) {
$result = array_merge($result, flattenArray($prefix, $value));
} else {
$result[] = "$prefix$value";
}
}
return $result;
}