help inserts empty data from xml to mysql php database

I have a program in PHP that reads a xml and inserts the data into a mysql database but when I run it inserts only empty data. Next I put the xml and the code that I am using:

XML

<?xml version="1.0" encoding="utf-8"?>

      <InvoiceControl>
        <InvoiceAuthorization>320001</InvoiceAuthorization>
        <AuthorizationPeriod>
          <StartDate>2014-01-13</StartDate>
          <EndDate>2015-01-13</EndDate>
        </AuthorizationPeriod>
        <AuthorizedInvoices>
          <Prefix>PR</Prefix>
          <From>769700</From>
          <To>769702</To>
        </AuthorizedInvoices>
      </InvoiceControl>
      <InvoiceSource>
        <IdentificationCode>CO</IdentificationCode>
      </InvoiceSource>
      <SoftwareProvider>
        <ProviderID>90030</ProviderID>
        <SoftwareID>a9c0758b-735b-4951</SoftwareID>
      </SoftwareProvider>
      <SoftwareSecurityCode>8f9d9d22d4c3381a0282e8f3beb</SoftwareSecurityCode>

  </ExtensionContent>
</UBLExtension>
<UBLExtension>
  <ExtensionContent />
</UBLExtension>

PHP CODE

    <?php
$conn = mysqli_connect("localhost", "root", "", "facturacion");

$affectedRow = 0;
libxml_use_internal_errors ( true ); 
$xml = simplexml_load_file("PI-Pirelli-001-7697004318.xml") or die("Error: Cannot create object");

foreach ($xml->children() as $row) {


$DIN_INVOICE_AUTHORIZATION = $row->InvoiceAuthorization;
$DDA_START_DATE = $row->StartDate;
$DDA_END_DATE = $row->EndDate;
$DVC_PREFIX = $row->Prefix;
$DIN_FROM = $row->From;
$DIN_TO = $row->To;
$DCH_IDENTIFICATION_CODE = $row->IdentificationCode;
$DIN_PROVIDERID = $row->ProviderID;
$DVC_SOFTWAREID = $row->SoftwareID;
$DVC_SOFTWARESECURITYCODE = $row->SoftwareSecurityCode;

    $sql = "INSERT INTO fed_ublextensions(DIN_INVOICE_AUTHORIZATION, DDA_START_DATE, DDA_END_DATE, DVC_PREFIX, DIN_FROM, DIN_TO, DCH_IDENTIFICATION_CODE, DIN_PROVIDERID, DVC_SOFTWAREID, DVC_SOFTWARESECURITYCODE) VALUES ('" . $DIN_INVOICE_AUTHORIZATION . "','" . $DDA_START_DATE . "','" . $DDA_END_DATE . "','" . $DVC_PREFIX . "','" . $DIN_FROM . "','" . $DIN_TO . "','" . $DCH_IDENTIFICATION_CODE . "','" . $DIN_PROVIDERID . "','" . $DVC_SOFTWAREID . "','" . $DVC_SOFTWARESECURITYCODE . "')";

    $result = mysqli_query($conn, $sql);

    if (! empty($result)) {
        $affectedRow ++;
    } else {
        $error_message = mysqli_error($conn) . "n";
    }
}
?>
<h2>Insert XML Data to MySql Table Output</h2>

<?php
if ($affectedRow > 0) {
    $message = $affectedRow . " records inserted";
} else {
    $message = "No records inserted";
}

?>
<style>
body {
        max-width: 550px;
        font-family: Arial;
}

.affected-row {
        background: #cae4ca;
        padding: 10px;
        margin-bottom: 20px;
        border: #bdd6bd 1px solid;
        border-radius: 2px;
        color: #6e716e;
}

.error-message {
        background: #eac0c0;
        padding: 10px;
        margin-bottom: 20px;
        border: #dab2b2 1px solid;
        border-radius: 2px;
        color: #5d5b5b;
}
</style>
<div class="affected-row">
    <?php  echo $message; ?>
</div>
<?php if (! empty($error_message)) { ?>
<div class="error-message">
    <?php echo nl2br($error_message); ?>
</div>
<?php } ?>