How to Properly Parse Nested JSON Data in PHP?

Parsing JSON Objects in PHP with json_decode

When attempting to retrieve weather data from a JSON-formatted web service, you may encounter challenges. A common PHP request code that doesn't succeed:

$url = "http://www.worldweatheronline.com/feed/weather.ashx?q=schruns,austria&format=json&num_of_days=5&key=8f2d1ea151085304102710";
$json = file_get_contents($url);
$data = json_decode($json, TRUE);
echo $data[0]->weather->weatherIconUrl[0]->value;

To understand the issue, let's examine the JSON data you received:

{
  "data": {
    "current_condition": [...],
    "request": [...],
    "weather": [
      {
        "date": "2010-10-27",
        "precipMM": "0.0",
        "tempMaxC": "3",
        "tempMaxF": "38",
        "tempMinC": "-13",
        "tempMinF": "9",
        "weatherCode": "113",
        "weatherDesc": [{ "value": "Sunny" }],
        "weatherIconUrl": [{ "value": "http://www.worldweatheronline.com/images/wsymbols01_png_64/wsymbol_0001_sunny.png" }],
        "winddir16Point": "N",
        "winddirDegree": "356",
        "winddirection": "N",
        "windspeedKmph": "5",
        "windspeedMiles": "3"
      },
      ...
    ]
  }
}

Notice that the weather data is nested within the "data" object. Therefore, to correctly parse the JSON, you need to modify your code:

$url = 'http://www.worldweatheronline.com/feed/weather.ashx?q=schruns,austria&format=json&num_of_days=5&key=8f2d1ea151085304102710';
$content = file_get_contents($url);
$json = json_decode($content, true);

foreach ($json['data']['weather'] as $item) {
    print $item['date'];
    print ' - ';
    print $item['weatherDesc'][0]['value'];
    print ' - ';
    print '<img src="' . $item['weatherIconUrl'][0]['value'] . '" border="0" alt="" />';
    print '<br>';
}

Setting the second parameter of json_decode to true gives you an array, allowing you to access data using array indexing. The JSONview Firefox extension can also help visualize JSON structures and simplify parsing.

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