Como pesquisar no índice de texto completo usando php no mongodb

<?php
$result = $db->command(
    array(
        'text' => 'bar', //this is the name of the collection where we are searching
        'search' => 'hotel', //the string to search
        'limit' => 5, //the number of results, by default is 1000
        'project' => Array( //the fields to retrieve from db
            'title' => 1
        )
    )
);