在php中用json_encode打印foreach循环

"option": [
    {
      "poOptionGroup": "11",
      "optGrpID": "11",
      "optGrpName": "Choose Backing Material"
    },
    {
      "optID": "40",
      "optName": "Black (Plexiglass)",
      "optPriceDiff": "0"
    },
    {
      "optID": "41",
      "optName": "Clear (Plexiglass)",
      "optPriceDiff": "18"
    },
    {
      "optID": "218",
      "optName": "Neon Stand Off",
      "optPriceDiff": "18"
    },
    {
      "optID": "219",
      "optName": "White Plastic",
      "optPriceDiff": "18"
    }
  ],
  "option": [
    {
      "poOptionGroup": "13",
      "optGrpID": "13",
      "optGrpName": "Any notes you want to include with your order"
    },
    {
      "optID": "174",
      "optName": "NO Thanks",
      "optPriceDiff": "0"
    },
    {
      "optID": "175",
      "optName": "YES OUTDOOR",
      "optPriceDiff": "170"
    }
  ],
  "SPIN3": [
    {
      "poOptionGroup": "56",
      "optGrpID": "56",
      "optGrpName": "Upgrade to OUTDOOR"
    },
    {
      "optID": "44",
      "optName": "",
      "optPriceDiff": "20.02"
    }
  ]

$product=array();   
        foreach($query as $q){
            $product['optGrpID']= $q['optGrpID'];
            $product['optGrpName'] = $q['optGrpName'];
            $product['poOptionGroup'] = $q['poOptionGroup'];
            $opt_id=$product['optGrpID'];
                $string=  sql("select optID, optName, optPriceDiff from options where optGroup='$opt_id' ");
                foreach ($string as $k=>$s){
                    $product['options']['optID']=$s['optID'];
                    $product['options']['optName']=$s['optName'];
                    $product['options']['optPriceDiff']=$s['optPriceDiff'];
                }
        }