Iterator that assigns subvalue as key - php

Question

Currently I'm looping through a quite large data set. This multidimensional array needs to be grouped by specific array values of its sub arrays. As this is a holiday project, I want to do deepen my knowledge and make more use of PHPs Iterators. Point is, that I don't know how to transform a numeric multi-dimensional Array into a multi-dimensional array with associative keys.
Shortened example (GeoJSON to Array)
array (size=4)
'type' => string 'FeatureCollection' (length=17)
'features' => // THIS is the actual array
array (size=207)
0 => // Sub-Arrays like this one are repeating
array (size=5)
'type' => string 'Feature' (length=7)
'geometry' =>
array (size=2)
'type' => string 'LineString' (length=10)
'coordinates' =>
array (size=410)
0 =>
array (size=2)
0 => float 16.359980888872
1 => float 48.208437070943
// etc.
'geometry_name' => string 'SHAPE' (length=5)
'properties' =>
array (size=5)
'OBJECTID' => int 273
// This/"LBEZEICHNUNG" is the part I want to order/summon
// all further "geometry"-parts by
'LBEZEICHNUNG' => string '13A, 2, 86, U3' (length=1)
'LTYP' => string '1' (length=1)
'LTYPTXT' => string 'Tramway' (length=12)
'SE_ANNO_CAD_DATA' => null
'id' => int 1
The features array is what holds the actually looped datasets. And LBEZEICHNUNG are the values (single or comma separated) I want to sort/order by.
To make an example:
// Original values:
'LBEZEICHNUNG' => string '13A, 2, 86, U3'
// Now split them and push the features into new keys that have those values:
'13A' => array(
0 => // Sub-Arrays like this one are repeating
array (size=5)
'type' => string 'Feature' (length=7)
'geometry' =>
array (size=2)
'type' => string 'LineString' (length=10)
'coordinates' =>
array (size=410)
0 =>
array (size=2)
0 => float 16.359980888872
1 => float 48.208437070943
// etc.
'geometry_name' => string 'SHAPE' (length=5)
'properties' =>
array (size=5)
// "OBJECTID" now is obsolete
// "LBEZEICHNUNG" is now obsolete
'LTYP' => string '1' (length=1)
'LTYPTXT' => string 'Tramway' (length=12)
'SE_ANNO_CAD_DATA' => null
// "id" now is obsolete as well
),
"2" => // gets the same values as "13A"
// same goes for "86" and "U3"
Now every sub array that would have either 13A, 2, 86 or U3 in ["properties"]["LBEZEICHNUNG"], would push its geometry to the end of the already existing subarray/sub-Iterator.
So far I only got a basic recursive Iterator set up, that runs through all leaves.
$data = new \RecursiveArrayIterator( $fileContents );
foreach( new \RecursiveIteratorIterator( $data ) as $key => $value )
{
// foo. bar. dragons.
}
Point is that I can't really figure out how to assign new keys from values in the Iterator. I already tried using a RecursiveFilterIterator and failed gracefully as its simply not intended to do this. Quite frankly: I'm lost as I either can't find the right Iterator to use or I simply ain't know enough about Iterators yet.
I got a working solution with nested foreach-es pushing into another Array. As this is my holiday project I want to learn, hence the Iterator solution, which I hope is more maintainable in the long turn.
Edit: Link to the original Geo-JSON data set CC-BY-SA 3.0/AUT - Data provided by the City of Vienna. Other formats can be found here.

Answer 1

If I understood correctly, you want to sort/ or group the array based on that "LBEZEICHNUNG" key, and use PHP iterators. In order to do that, you have to traverse the entire array, and build a new one that holds the values grouped by that key. This is simple foreach logic.
Iterators shine when you want to traverse a data collection and fetch the data during traversal (or alter it).
In this case, you are fetching the data outside of the iterator (json_decode ?), so that makes iterators kind of pointless - unless you need to do more than just sorting. If you do, I'd suggest you store that data in a format that allows you to easily fetch sorted sets, like a database, then you can use iterators to their full potential.
One way to group the routes is to use basic OOP:
class Route{
protected $trams = array();
// add other route properties (type, geometry etc.)
public function assignTo(Tram $line){
if(!in_array($line, $this->trams, true))
$this->trams[] = $line;
}
public function getTrams(){
return $this->trams;
}
}
class Tram{
public $name;
protected $routes = array();
public function __construct($name){
$this->name= $name;
}
public function addRoute(Route $route){
$this->routes[] = $route;
$route->assignTo($this);
}
public function getRoutes(){
return $this->routes;
}
}
Example:
$trams = array();
foreach($data as $routeData){
$route = new Route();
$tramNames = explode(', ', $routeData['features']['properties']['LBEZEICHNUNG']);
foreach($tramNames as $name){
if(!isset($trams[$name]))
$trams[$name] = new Tram($name);
$trams[$name]->addRoute($route);
// set other route properties...
}
}

Answer 2

You can use usort to sort your multi-dimensional array based on sub-values:
$JSON = iconv('UTF-8', 'UTF-8//IGNORE', utf8_encode(file_get_contents("http://data.wien.gv.at/daten/geoserver/ows?service=WFS&request=GetFeature&version=1.1.0&srsName=EPSG:4326&outputFormat=json&typeName=ogdwien:OEFFLINIENOGD")));
$geoarray = json_decode($JSON, true);
$myarray = $geoarray["features"];
function cmp($a, $b) {
return $a["properties"]["LBEZEICHNUNG"] - $b["properties"]["LBEZEICHNUNG"];
}
usort($myarray, "cmp");
print_r($myarray);