<?php
$json = '{
  "models":
  {
    "items":
    [
      {
        "id": 5086952,
        "name": "K&K УАЗ",
        "categoryId": 166068,
        "prices":
        {
          "max": "3437",
          "min": "1371", 
          "avg": "2124",
          "curCode": "RUR",
          "curName": "руб."
        },
        "mainPhoto":
        {
          "url": "http://m...content-available-to-author-only...x.net/i?ctype=1&path=b0407143125_img_id2982751556581079079.jpg",
          "width": 700,
          "height": 660
        },
        "vendor": "K&K",
        "vendorId": 967139,
        "offersCount": 53,
        "isNew": 0,
        "rating": 4,
        "gradeCount": 20,
        "reviewsCount": 0,
        "link": "http://m...content-available-to-author-only...x.ru/model.xml?CMD=-RR=9,0,0,0-PF=1801946~EQ~sel~12129354-PF=2142397915~EQ~sel~1728823252-VIS=8070-CAT_ID=922145-EXC=1-PG=2&modelid=5086952&hid=166068",
        "isGroup": true,
        "modificationsCount": 1
      },
      {
        "id": 5087157,
        "name": "Replica B58",
        "categoryId": 166068,
        "prices":
        {
          "max": "10208",
          "min": "2850",
          "avg": "4774",
          "curCode": "RUR",
          "curName": "руб."
        },
        "mainPhoto":
        {
          "url": "http://m...content-available-to-author-only...x.net/i?path=b0903150122_img_id5220150240620638559.jpg",
          "width": 475,
          "height": 445
        },
        "vendor": "Replica",
        "vendorId": 967138,
        "offersCount": 1076,
        "isNew": 0,
        "rating": 5,
        "gradeCount": 30,
        "reviewsCount": 0,
        "link": "http://m...content-available-to-author-only...x.ru/model.xml?CMD=-RR=9,0,0,0-PF=1801946~EQ~sel~12129351-PF=2142397915~EQ~sel~1899859412-VIS=8070-CAT_ID=922145-EXC=1-PG=2&modelid=5087157&hid=166068",
        "isGroup": true,
        "modificationsCount": 27
      }
    ],
    "page": 1,
    "total": 13177,
    "count": 2
  }
}';
$my_obj = json_decode($json);
#Array предметов в категории:
var_dump($my_obj->models->items);

#Например стоимость.
foreach ($my_obj->models->items as $item){
	echo "{$item->prices->avg} {$item->prices->curName}\n";
}
?>