I've just started to use these scripts, but I'm puzzled by the fact that purpleair-inc.php seems to have two identical file_get_contents() calls to the API on lines 41 and 62:
$pajson = file_get_contents("https://api.purpleair.com/v1/sensors/$sensorid?api_key=$PurpleAirAPI",0,$STRcontext);
and a $fname location (line 61) when there is no caching that I can see.
Now that newcomers have to pay for PurpleAir API calls a cache might be useful: see
here (you don't have to run the cron every 5 minutes)
But I would probably cache at
$fname = './cache/purpleair-'.$sensorid.'.json';
for a standard Saratoga setup.