How to get second layer output from XML and convert to php variable ?

Hi,

I have the following scripts :

<?

$xml="<whmcsapi>
<action>getinvoice</action>
<result>success</result>
<invoiceid>242347</invoiceid>
<invoicenum></invoicenum>
<userid>25209</userid>
<date>2017-12-21</date>
<duedate>2018-01-11</duedate>
<datepaid>0000-00-00 00:00:00</datepaid>
<lastcaptureattempt>0000-00-00 00:00:00</lastcaptureattempt>
<subtotal>50.00</subtotal>
<credit>0.00</credit>
<tax>3.00</tax>
<tax2>0.00</tax2>
<total>53.00</total>
<balance>53.00</balance>
<taxrate>6.00</taxrate>
<taxrate2>0.00</taxrate2>
<status>Unpaid</status>
<paymentmethod>banktransfer</paymentmethod>
<notes></notes>
<ccgateway></ccgateway>
     <items>
                   <item>
                                <id>304494</id>
                                <type>Domain</type>
                                <relid>52025</relid>
                                <description>Domain Renewal - xxx.com - 1 Year/s (11/01/2018 - 10/01/2019)</description>
                                <amount>50.00</amount>
                                <taxed>1</taxed>
                  </item>
     </items>
<transactions></transactions>
</whmcsapi>";


$content .= '<table border="1" cellpadding="5" style="border-collapse: collapse;border: 1px solid #cacaca">';

$content .= '<tr><th colspan="2" bgcolor="thistle">ITEMS '.print_r($xml).'</th></tr>';
foreach ($xml['items']['item'] as $key => $value) {

  $content .= '<tr><td><b>Description</b></td><td>'.$value['description'].'</td></tr>';
  $content .= '<tr><td><b>Amount</b></td><td>'.$value['amount'].'</td></tr>';
}
	

	$content .= '</table>';

return $content;
?>

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But i received the following error :

Warning: Illegal string offset 'items' in /home/internet/public_html/test/teststring4.php on line 42

Warning: Illegal string offset 'item' in /home/internet/public_html/test/teststring4.php on line 42

Warning: Invalid argument supplied for foreach() in /home/internet/public_html/test/teststring4.php on line 42


May i know how to get the variable inside the "items" and "item" ?

I have tried "foreach ($xml['items']['item'] as $key => $value)" but it produce the above error.

Hope anybody can help me by providing the correct script.