PHP JSON Group pelo mesmo valor

<?php
$json = array();

foreach ($array as $idx => $data) {
    //Id is not exists in json,create new data 
    if( !array_key_exists($data['Id'], $json) ){//Id is unique in db,use Id for index ,you can find it easily
        $json[$data['Id']]=array(
            'Id'  =>$data['Id'],
            'Name'=>$data['Name'],
            'Value'=>array(
                    $data['Date']=>$data['Value']
                )
        );
        continue;
    }

    //Id is exists in json, append value
    $json[$data['Id']]['Value'][$data['Date']] =$data['Value'];
}
$json = json_encode($json);