Get inside the response with php-echonest

Hi, I'm trying to use the php wrapper at- https://github.com/bshaffer/php-echonest-api

Using the examples I can for example get Biographies for Radiohead.

But what if I only want to know what site they were published at?

This code

print("$artistApi = $echonest->getArtistApi();
$artistApi->setName('Radiohead');
$bios   = $artistApi->getBiographies(2);
print_r($bios);");

Gives me the two first Biographies for Radiohead:

Array
(
    [0] => Array
        (
            [text] => It's usually safe as milk to assume that bands who ...
            [site] => trouserpress
            [url] => http://trouserpress.com/entry.php?a=radiohead
            [license] => Array
                (
                    [type] => unknown
                    [attribution] => trouserpress
                    [attribution-url] => http://trouserpress.com/entry.php?a=radiohead
                    [url] => n/a
                    [version] => n/a
                )

            [truncated] => 1
        )

    [1] => Array
        (
            [text] => Radiohead was one of the few alternative bands of the ...
            [site] => mtvmusic
            [url] => http://www.mtvmusic.com/radiohead
            [license] => Array
                (
                    [type] => unknown
                    [attribution] => n/a
                    [attribution-url] => http://www.mtvmusic.com/radiohead
                    [url] => n/a
                    [version] => n/a
                )

            [truncated] => 1
        )

)

I would have imagined that I could do something like:

$bios   = $artistApi->getBiographies(2)->site;

to just get the site they were published at.

Can anyone give me a hint how this is done?