You can also use this function to repair xml, for example if stray ampersands etc are breaking it:

<?php
$xml = tidy_repair_string($xml, array(
    'output-xml' => true,
    'input-xml' => true
));
?>

The docs referenced at http://tidy.sourceforge.net/docs/quickref.html above state that the configuration option 'sort-attributes' is an enumeration of 'none' and 'alpha', thereby specifying that strings of either form are the acceptable values.  This may not be the case, however - on my system, the option was not honored until I set it to true.  This may also be the case with other options, so experiment a bit.  The output of tidy::getConfig() may be useful in this regard.

Using tidy is very simple to fix a broken ods/odt document
I wrote the following code to be run from command line

<?php
$zip = new ZipArchive();
if ($zip->open($argv[1])) {
  $fp = $zip->getStream('content.xml'); //file inside archive
  if(!$fp)
    die("Error: can't get stream to document file");
  $stat = $zip->statName('content.xml');
  $buf = ""; //file buffer
  ob_start(); //to capture CRC error message
    while (!feof($fp)) {
      $buf .= fread($fp, 2048); 
    }
    $s = ob_get_contents();
  ob_end_clean();
  fclose($fp);
  $zip->close();
  $config = array(
      'indent' => true,
      'clean' => true,
      'input-xml'  => true,
      'output-xml' => true,
      'wrap'       => false
  );
  $tidy = new Tidy();
  $xml = $tidy->repairstring($buf, $config);
  $array=split("\n",$xml);
  $file=tempnam("/tmp","xml");
  $fp=fopen($file,"rw+");
  foreach ($array as $key=>$value) {
    fwrite($fp,trim($value),strlen(trim($value)));
    if ($key==0) {
      fwrite($fp,"\n");
    }
  }
  fclose($fp);
  if ($zip->open($argv[1]) === TRUE) {
    $zip->deleteName('content.xml');
    $zip->addFile($file, 'content.xml');
    $zip->close();
    echo 'recovery complete';
  } else {
    echo 'recovery failed';
  }
  unlink($file);
}
?>

save it to a file called fixdoc and invoke as:
php fixdoc yourbrokendoc

for your safety, please work on a copy of your doc.