I have the following string:
{\"Coords\":[{\"Accuracy\":\"65\",\"Latitude\":\"53.277720488429026\",\"Longitude\":\"-9.012038778269686\",\"Timestamp\":\"Fri J
$decoded_traces is an object. You cannot simply echo an object, because that makes no sense.
$decoded_traces
echo
If you want to debug the object, use var_dump($decoded_traces).
var_dump($decoded_traces)