<?php
$m = new MongoClient();
$res = $m->demo->poiConcat->aggregate( [
[ '$match' => [ 'ts' => new MongoRegex( '/^cuisine=/' ) ] ],
[ '$unwind' => '$ts' ],
[ '$match' => [ 'ts' => new MongoRegex( '/^cuisine=/' ) ] ],
/* Now we group on the ts */
[ '$group' => [ '_id' => '$ts' ] ],
] );
var_dump( $res['result'] );
?>