www.free-kassa.ru/api.php?merchant_id=7012&s=c4ca4...
<?xml version="1.0" encoding="UTF-8" ?>
<root>
<answer>info</answer>
<desc>Merchant balance</desc>
<balance>12.73</balance>
</root>
//$xml=file_get_contents("http://www.free-kassa.ru/api.php?merchant_id=7012&s=c4ca4238a0b923820dcc509a6f75849b&action=get_balance");
$xml = <<<EOT
<?xml version="1.0" encoding="UTF-8" ?>
<root>
<answer>info</answer>
<desc>Merchant balance</desc>
<balance>12.73</balance>
</root>
EOT;
$data=simplexml_load_string($xml);
$balance=$data->balance;
print $balance;