MongoDB indexing in PHP

PHP Mongodb Indexing:
It is not so hard to make index in Bigdata database such like MongoDB. Take look following bellow.

<?php

$c = new MongoCollection($db, 'foo');

// Create an index on 'A' ascending
$AscIndex = array('A' => 1);
$c->createIndex($AscIndex);

// Create an index on 'A' descending
$DscIndex = array('A' => -1);
$c->createIndex($DscIndex);

// Create a unique index on 'a_row_index'
$a_row_index = array('a_row_index' => 1), array('unique' => true);
$cIndex -> createIndex($a_row_index);

// create a compound index on 'XY' ascending and 'YX' descending
$XyYx = array('XY' => 1, 'YX' => -1);
$cIndex -> createIndex($XyYx);

?>