$str = '{"param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"}{"param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"}{"param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"}';
$arr = explode('}{', $str);
print_r($arr);
Array
(
[0] => {"param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"
[1] => "param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"
[2] => "param1": "value1","param1": "value1","param1": "value1","param1": {},"param1": "value1"}
)
+немного допилить напильником каждый элемент массива до нормальной json-строки и дальше как обычно
изврат, конечно