If you are not sure where a particular value you entered into the IPTC block in photoshop or any other software is being stored, simply run a foreach loop thru the block and find out:

(Insert a new paragraph in the beggening of the first echo)

$size = GetImageSize ("testimg.jpg", &$info);
$iptc = iptcparse($info["APP13"]);

foreach($iptc as $key => $value)
{
    echo "<b>IPTC Key:</b> $key <b>Contents:</b> ";
    foreach($value as $innerkey => $innervalue)
    {
        if( ($innerkey+1) != count($value) )
            echo "$innervalue, ";
        else
            echo "$innervalue";
    }
}