<?php
$m = new MongoClient();

$res = $m->demo->poiConcat->aggregate( [
    [ '$match' => [ 'ts' => new MongoRegex( '/^cuisine=/' ) ] ],
    [ '$unwind' => '$ts' ],
    /* Match again to get rid of all the useless ts */
    [ '$match' => [ 'ts' => new MongoRegex( '/^cuisine=/' ) ] ],
] );

var_dump( $res['result'] );
?>