Jul
07
2017
PHP Sorting Iterators

Iterator

a few months ago, I wrote an article on RecursiveDirectoryIterator, you can find the article here: PHP Recursive Directory File Listing . If you run the code example, you ‘ll see that the output is not sorted.

Object

Recursive Iterator is actually an object, a special object that we can perform iterations on sequence (collection) of data. So it is a little difficult to sort them using known php functions. Let me give you an example:

$Iterator = new RecursiveDirectoryIterator('./');
foreach ($Iterator as $file)
    var_dump($file);
object(SplFileInfo)#7 (2) {
  ["pathName":"SplFileInfo":private]=>
  string(12) "./index.html"
  ["fileName":"SplFileInfo":private]=>
  string(10) "index.html"
}

You see here, the iterator is an object of SplFileInfo class.

Internet Answers

Unfortunately stackoverflow and other related online results provide the most complicated answers on this matter. Of course this is not stackoverflow’s error, and it is really a not easy subject to discuss or understand, but personally I dont get the extra fuzz (complexity) on some of the responses.

Back to basics

So let us go back a few steps and understand what an iterator really is. An iterator is an object that we can iterate! That means we can use a loop to walk through the data of an iterator. Reading the above output you can get (hopefully) a better idea.

We can also loop the Iterator as a simply array.

eg.

$It = new RecursiveDirectoryIterator('./');
foreach ($It as $key=>$val)
    echo $key.":".$val."n";

output:

./index.html:./index.html

Arrays

It is difficult to sort Iterators, but it is really easy to sort arrays!
We just need to convert the Iterator into an Array:

// Copy the iterator into an array
$array = iterator_to_array($Iterator);

that’s it!

Sorting

For my needs I need to reverse sort the array by key (filename on a recursive directory), so my sorting looks like:

krsort( $array );

easy, right?

Just remember that you can use ksort before the array is already be defined. You need to take two steps, and that is ok.

Convert to Iterator

After sorting, we need to change back an iterator object format:

// Convert Array to an Iterator
$Iterator = new ArrayIterator($array);

and that’s it !

Full Code Example

the entire code in one paragraph:

<?php
// ebal, Fri, 07 Jul 2017 22:01:48 +0300

// Directory to Recursive search
$dir = "/tmp/";

// Iterator Object
$files =  new RecursiveIteratorIterator(
          new RecursiveDirectoryIterator($dir)
          );

// Convert to Array
$Array = iterator_to_array ( $files );
// Reverse Sort by key the array
krsort ( $Array );
// Convert to Iterator
$files = new ArrayIterator( $Array );

// Print the file name
foreach($files as $name => $object)
    echo "$namen";

?>
Tag(s): php, iterator