The Array must be:
{
"results":[
{
"signal_id":11328555834,
"dec_lat":52,
"dec_long":8
},
{
"signal_id":11328549683,
"dec_lat":53,
"dec_long":9
},
{
"signal_id":11328549682,
"dec_lat":12,
"dec_long":6
}
]
}
$dec_lat = $data["results"][count($data["results"])-1]["dec_lat"];