Restfull JSON Array Help

Hi,
Please can someone give me some advice, I have setup an API which is working but cant seem to get some of the json data.
this is the data being posted(cant be changed coming from out side source)
{
"code": "VET002",
"store": "DBNG0024",
"items": [
{
"code": "1",
"descr": "Yoghurt",
"value": "66",
"qty": "3",
"dept": "1"
},
{
"code": "25",
"descr": "Red Bull",
"value": "44",
"qty": "2",
"dept": "2"
},
{
"code": "23",
"descr": "Lipton Lemon",
"value": "72",
"qty": "6",
"dept": "2"
}
]
}
this is how I'm reading the data
$code = $this->post('code');
$store_code = $this->post('store');
$total = $this->post('total');
how would i read the items values.
Thank you