Description:
------------
See the page at http://us3.php.net/manual/en/mongocollection.remove.php

Scroll down to Example #1

$uranium->remove(array('type' => 94), array("justOne" => true));

$uranium is undefined in the example. It needs to be a MongoCollection object for 
the example to be functional.

Test script:
---------------
<?php

$radioactive = $db->radioactive;

// count how much more plutonium there is
$remaining = $radioactive->count(array('type' => 94));

$halflife = $remaining/2;

// remove half of it
while ($halflife > 0) {
    $uranium->remove(array('type' => 94), array("justOne" => true));
    $halflife--;
}

?>