Query operators don't have to start with $ anymore:

<?php
$m = new Mongo;
$c = $m->selectCollection( 'dbname', 'colname' );
$r = $c->find( array( "fieldname" => array( "$gte" => 42 ) ) );
?>
ini_set( 'mongo.cmd', '@' );

<?php
$m = new Mongo;
$c = $m->selectCollection( 'dbname', 'colname' );
$r = $c->find( array( "fieldname" => array( "@gte" => 42 ) ) );
?>