非法字符串偏移'距离'

        <!-- I want to see the content from units tag at json file, and its don't work.  -->

            $json = file_get_contents('https://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20weather.forecast%20where%20woeid%20in%20(select%20woeid%20from%20geo.places(1)%20where%20text%3D%22' . "$oras" . '%2C%20' . "$tara" . '%22%20)%20and%20u%3D' . "%27$afisaj%27" . '&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys');

            $obj = json_decode($json);

                echo "<pre>";
                print_r($obj);
                echo "</pre>";

                echo "<br><hr><br>";

                foreach ($obj->query->results->channel->units as $key => $value) {
                    var_dump($key);
                    echo $key['distance']; // there is the problem
                    echo $key . "&nbsp;&nbsp;&nbsp;" . "<br><br>";
                    echo $value . "&nbsp;&nbsp;&nbsp;";
                }

                echo "<br><hr><br>";

                foreach ($obj->query->results->channel->item->forecast as $key) {
                    echo '<b style="color:red;">Low:</b>' . $key->low .
                    '<b style="color:blue;">High:</b>' . $key->high .
                    '<b style="color:green;">Date</b>' . $key->date .
                    '<b style="color:purple;">Day</b>' . $key->day .
                    '<b style="color:yellow;">Text</b>' . $key->text .
                    "<br>";
                }
?>

       The content at $obj, i want to obtain data from units:

stdClass Object ( [query] => stdClass Object ( [count] => 1 [created] => 2016-05-05T19:15:02Z [lang] => en-US [results] => stdClass Object ( [channel] => stdClass Object ( [units] => stdClass Object ( [distance] => mi [pressure] => in [speed] => mph [temperature] => F )

To expand on my answer above...

foreach works one of two ways:

foreach($variable as $thing)
{
    // Do something
}

foreach($variable as $index=>$thing)
{
    // Do something
}

In both examples, $variable must be an array or object, and it will iterate over $variable.

In the first example, $thing will be the current value (the current element of the object or array). In the second example, $index is the index of the object or array (and it is automatically assigned), and $thing is the current value (again, the current element of the object or array.)

So, let's say this is your array

$variable = ['foo', 'bar', 'baz'];
foreach($variable as $thing)
{
    echo $thing.'<br/>';
}

You would get:

foo
bar
baz

If instead you used the second version of foreach....

$variable = ['foo', 'bar', 'baz'];
foreach($variable as $index=>$thing)
{
    echo 'Element '. $index . ' = ' $thing.'<br/>';
}

You'd get:

Element 0 = foo
Element 1 = bar
Element 2 = baz

The important takeaway from the second form of foreach is that $index will never be an array. It might be a numeric index, it might be a string index. It will never be an array.

So, in your example $key['distance'] will always say that it's an illegal offset, because $key is not an array to begin with.

Edit: Using your example above:

foreach ($obj->query->results->channel->units as $key => $value) {
    if($key == 'distance') {
        echo $key . "&nbsp;&nbsp;&nbsp;" . "<br><br>";
        echo $value . "&nbsp;&nbsp;&nbsp;";
    }
}

Now, if it turns out the value for the key 'distance' is not a string, it's going to have a different error for you.