How do I use PHP to read the JSON output for ALERTS from Wunderground?

Question

It seems that reading the 'conditions' JSON output from Wunderground is very different than readying the output from 'alerts'. Below is a simplified version of my code.

$json_stringalert = file_get_contents("http://api.wunderground.com/api/myKey/alerts/q/MO/Kansas_City.json");
$parsed_jsonalert = json_decode($json_stringalert);
$description = $parsed_jsonalert->{'alerts'}->{'description'}; 
echo "${description}

The echo is blank, and there are no errors. The output of the the URL looks in part like this;

{
  "response": {
  "version":"0.1",
  "termsofService":"http://www.wunderground.com/weather/api/d/terms.html",
  "features": {
  "alerts": 1
  }
    }
        ,"query_zone": "037",
    "alerts": [
        {
        "type": "FIR",
        "description": "Fire Weather Warning",
        "date": "10:27 am CST on March 2, 2017",
        "date_epoch": "1488472020",
        "expires": "6:00 PM CST on March 02, 2017",
        "expires_epoch": "1488499200",
        "tz_short":"CST",
        "tz_long":"America/Chicago",
        "message": "\u000A...Red flag warning in effect until 6 PM CST this evening for\u000Abreezy northwest winds and low relative humidity values for fire \u000Aweather zones 020, 021, 025, 028, 029, 030, 037, 038, 043, 044, \u000A045, 053, 054, 057, 060, 102, 103, 104, and 105...\u000A\u000AThe National Weather Service in Kansas City/Pleasant Hill has\u000Aissued a red flag warning, which is in effect until 6 PM CST this\u000Aevening. \u000A\u000A* Affected area...fire weather zones 025, 057, 060, 102, 103, \u000A 104, and 105.Fire weather zones 020, 021, 028, 029, 030, 037, \u000A 038, 043, 044, 045, 053, and 054. \u000A\u000A* Wind...sustained northwest winds of 20 mph with higher gusts are\u000A expected this afternoon. \u000A\u000A* Humidity...relative humidity values will fall into the low to\u000A middle 20 percent range. \u000A\u000A* Impacts...any fires that develop will likely spread rapidly. \u000A Outdoor burning is not recommended.\u000A\u000APrecautionary/preparedness actions...\u000A\u000AA red flag warning means that critical fire weather conditions\u000Aare either occurring now, or will shortly. A combination of\u000Astrong winds, low relative humidity, and warm temperatures can\u000Acontribute to extreme fire behavior.\u000A\u000A\u000A\u000ACramer\u000A\u000A\u000A",
        "phenomena": "FW",
        "significance": "W", ...
and more below.

Can someone please help me write the code to use the 'description' and other output?

alerts is an array so you'll have to access description for each using a loop — mickadoo, Mar 02 '17 at 22:15

score 1 · Answer 1 · answered Mar 02 '17 at 22:14

1

$alert_array = $parsed_jsonalert->alerts; 
foreach($alert_array as $alert) {
    echo $alert->description;
}

answered Mar 02 '17 at 22:14

Lynne

150
12

score 0 · Accepted Answer · answered Mar 02 '17 at 22:26

In your JSON output the Alerts key is an array so $json->alerts->description doesn't access anything in particular. I'm assuming you want all alerts here and not just a specific key ($json->alerts[0]->description) so you would need to loop over your data like so:

function getAlerts($jsonString)
{
  $parsedObj = json_decode($jsonString);

  // This is the entire array of alert objects.
  $alertsArray = $parsedObj->alerts;

  // This next section is only necessary if you want to extract specific 
  // keys to be returned instead of the entire array of objects. If you
  // want everything than just return the $alertsArray variable.
  $alerts = array();

  foreach ($alertsArray as $alert) {
    // Add single key to alerts return array.
    // alternatively here is where you would build a filtered array
    // of values to return if you need more than one.
    $alerts[] = $alert->description;
  }
  return $alerts;
}
$file = file_get_contents("http://api.wunderground.com/api/myKey/alerts/q/MO/Kansas_City.json");
$alerts = getAlerts($file);
echo implode("\n", $alerts);

How do I use PHP to read the JSON output for ALERTS from Wunderground?

2 Answers2