PHP says that this json is invalid because “object property name separator ':' expected”, can anyone see why=?iso-8859-1?Q?=3F?=

PHP says that this json is invalid because "object property name separator
':' expected", can anyone see why?

What's wrong with this json:
{ "items" : [
{"timestamp":"1372964400","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1373666400","value":"2","nid":"593141","platform":"-1"},{"timestamp":"1371398400","value":"1","nid":"34872","platform":"-1"},{"timestamp":"1374238800","value":"2","nid":"59251","platform":"-1"},{"timestamp":"1371902400","value":"1","nid":"79534","platform":"-1"},{"timestamp":"1373425200","value":"1","nid":"583657","platform":"-1"},{"timestamp":"1376251200","value":"4","nid":"701275","platform":"-1"},{"timestamp":"1371330000","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1372183200","value":"1","nid":"81447","platform":"-1"},{"timestamp":"1372348800","value":"2","nid":"83560","platform":"-1"},{"timestamp":"1373162400","value":"1","nid":"583657","platform":"-1"},{"timestamp":"1374174000","value":"2","nid":"607389","platform":"-1"},{"timestamp":"1371834000","value":"2","nid":"79534","platform":"-1"},{"timestamp":"1372723200","value":"1","nid":"190555","platform":"-1"},{"timestamp":"137
3385600","value":"2","nid":"590502","platform":"-1"},{"timestamp":"1375855200","value":"1","nid":"697831","platform":"-1"},{"timestamp":"1372312800","value":"1","nid":"81447","platform":"-1"},{"timestamp":"1373047200","value":"2","nid":"545517","platform":"-1"},{"timestamp":"1373929200","value":"3","nid":"605563","platform":"-1"},{"timestamp":"1375462800","value":"1","nid":"647466","platform":"-1"},{"timestamp":"1376434800","value":"5","nid":"704771","platform":"-1"},{"timestamp":"1371722400","value":"1","nid":"79534","platform":"-1"},{"timestamp":"1372240800","value":"1","nid":"82257","platform":"-1"},{"timestamp":"1372687200","value":"1","nid":"190555","platform":"-1"},{"timestamp":"1373367600","value":"1","nid":"590502","platform":"-1"},{"timestamp":"1374634800","value":"1","nid":"610377","platform":"-1"},{"timestamp":"1375812000","value":"1","nid":"697482","platform":"-1"},{"timestamp":"1372129200","value":"1","nid":"81157","platform":"-1"},{"timestamp":"1372287600","val
ue":"1","nid":"79568","platform":"-1"},{"timestamp":"1372989600","value":"1","nid":"40191","platform":"-1"},{"timestamp":"1373788800","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1375376400","value":"1","nid":"646893","platform":"-1"},{"timestamp":"1376420400","value":"1","nid":"704624","platform":"-1"},{"timestamp":"1371423600","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1372230000","value":"7","nid":"81447","platform":"-1"},{"timestamp":"1372413600","value":"1","nid":"118275","platform":"-1"},{"timestamp":"1373306400","value":"5","nid":"590502","platform":"-1"},{"timestamp":"1374264000","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1371960000","value":"1","nid":"79568","platform":"-1"},{"timestamp":"1372924800","value":"1","nid":"82456","platform":"-1"},{"timestamp":"1373558400","value":"3","nid":"590502","platform":"-1"},{"timestamp":"1375092000","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1376280000","value":"1","nid":"7
01529","platform":"-1"},{"timestamp":"1370044800","value":"1","nid":"68566","platform":"-1"},{"timestamp":"1371380400","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1372183200","value":"3","nid":"81457","platform":"-1"},{"timestamp":"1372352400","value":"1","nid":"83613","platform":"-1"},{"timestamp":"1373194800","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1375689600","value":"1","nid":"687547","platform":"-1"},{"timestamp":"1371902400","value":"2","nid":"59251","platform":"-1"},{"timestamp":"1372762800","value":"1","nid":"212931","platform":"-1"},{"timestamp":"1375977600","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1371322800","value":"2","nid":"59251","platform":"-1"},{"timestamp":"1372179600","value":"1","nid":"81457","platform":"-1"},{"timestamp":"1372345200","value":"2","nid":"83560","platform":"-1"},{"timestamp":"1373068800","value":"1","nid":"545517","platform":"-1"},{"timestamp":"1374163200","value":"1","nid":"607389","platform":
"-1"},{"timestamp":"1375470000","value":"1","nid":"647526","platform":"-1"},{"timestamp":"1376460000","value":"1","nid":"705149","platform":"-1"},{"timestamp":"1370278800","value":"1","nid":"57508","platform":"-1"},{"timestamp":"1371765600","value":"2","nid":"79568","platform":"-1"},{"timestamp":"1372690800","value":"1","nid":"212147","platform":"-1"},{"timestamp":"1373382000","value":"9","nid":"590502","platform":"-1"},{"timestamp":"1374674400","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1375819200","value":"1","nid":"697482","platform":"-1"},{"timestamp":"1371132000","value":"1","nid":"76647","platform":"-1"},{"timestamp":"1372143600","value":"1","nid":"81209","platform":"-1"},{"timestamp":"1372302000","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1373036400","value":"1","nid":"545500","platform":"-1"},{"timestamp":"1373886000","value":"1","nid":"59251","platform":"-1"},{"timestamp":"1375380000","value":"1","nid":"646893","platform":"-1"},{"timesta
mp":"1376427600","value":"1","nid":"704735","platform":"-1"},{"timestamp":"1370260800","value":"3","nid":"68984","platform":"-1"},{"timestamp":"1372240800","value":"1","nid":"82162","platform":"-1"},{"timestamp":"1372428000","value":"1","nid":"154915","platform":"-1"},{"timestamp":"1373364000","value":"6","nid":"590502","platform":"-1"},{"timestamp":"1374606000","value":"1","nid":"610377","platform":"-1"}]
}
when running json_decode on this string php returns null. i've checked
with every online php json_decoder and they decode it succesfully. i've
also tried with json_decode($json, TRUE); but the call also returns NULL
i'm on php version PHP 5.5.1-2+debphp.org~precise+2
I've checked what json_last_error_msg() has to say and it returned: object
property name separator ':' expected