如何在php中显示json解码数组？

$appUrl = "https://itunes.apple.com/us/rss/topfreeapplications/limit=400/genre=6014/json";

$appStore = new APPSTORE();
$json_appdata = $appStore->downloadApps($appUrl);

$appdata_array = json_decode($json_appdata, true);
//print_r($appdata_array);

foreach ($appdata_array["entry"] as $row) {
    print_r($row["im:name"]);
}

And then I got the following errors:

Notice: Undefined index: entry on line 13 which is in foreach.

Warning: Invalid argument supplied for foreach() on line 13

My question is: How do I do it so that I can display all the [im:name] elements? Thanks in advance!

You are missing the leading key. Try this:

foreach ($appdata_array['feed']['entry'] as $row) {
    print_r($row["im:name"]);
}

EDIT

To expand on the answer, I did a var_dump() of the returned/decoded data:

array (size=1)
  'feed' => 
    array (size=8)
      'author' => 
        array (size=2)
          'name' => 
            array (size=1)
              'label' => string 'iTunes Store' (length=12)
          'uri' => 
            array (size=1)
              'label' => string 'http://www.apple.com/itunes/' (length=28)
      'entry' => 
        array (size=400)
          0 => 
            array (size=12)
              'im:name' => 
                array (size=1)
                  'label' => string '2048' (length=4)
              'im:image' => 
                array (size=3)

Note that the leading key is feed.

Hope this helps! :)