解码扩展json从mongodb导出到php中的数组

I want to do the equivalent of json_decode() in php but with an extended json format exported by MongoDb

so the string I want to decode to a php array will be something like

{
"_id" : ObjectId("4fb136789c31e0b13f000000"),
"NumThings" : NumberInt(5), 
"StartDate" : ISODate("2017-05-17T17:08:01.621+0000")
}

I thought this was a more common problem, but have had no luck searching for an answer.

thanks in advance Scott