<?php
$m = new MongoClient;
$c = $m->demo->continent;
$r = $c->find( [
    'cities.population' => [ '$gte' => 11000000 ],
    'cities.dem' => [ '$gte' => 100 ],
] );

foreach( $r as $c ) {
    echo $c['name'], "\n";
    foreach( $c['cities'] as $city ) {
        echo '- ', $city['name'], ': ', $city['population'], ' - ', $city['dem'], "\n";
    }
}
?>