PHP SimpleXML Parsing Issue

Seems cause of encoding type utf-16 while content has utf-8.

So you need to change your encode type,

$string = '<?xml version="1.0" encoding="utf-16"?>
  <Response Version="1.0">
  <DateTime>2/13/2013 10:37:24 PM</DateTime>
  <Contact_ID>151-233-DD</Contact_ID>
  <Quote_ID>ojc332-ewied-23e3ed</Quote_ID>
  <Status>Failure</Status>
  <Reason>Incorrect Contact ID</Reason>
 </Response>'; 
$xml = simplexml_load_string(preg_replace('/(<\?xml[^?]+?)utf-16/i', '$1utf-8', $string)); 

Codepad DEMO.

Also It can be done using utf8_encode,

$xml = simplexml_load_string(utf8_encode($string)); 

You are constructing only one XML element (hint the name of the class). You need to load the whole string as a XML document. Here is how:

<?php

$result= <<<XML
<?xml version="1.0" encoding="utf-8"?>
<Response Version="1.0">
   <DateTime>2/13/2013 10:37:24 PM</DateTime>
   <Contact_ID>151-233-DD</Contact_ID>
   <Quote_ID>ojc332-ewied-23e3ed</Quote_ID>
   <Status>Failure</Status>
   <Reason>Incorrect Contact ID</Reason>
</Response>
XML;

$dom= new DOMDocument();
$dom->loadXML($result, LIBXML_NOBLANKS);

Then you can use the DOM interface to access the various components in the document.

e.g.

$dates = dom->getElementsByTagName('DateTime');

This will fetch an array containing all the DateTime elements.

EDIT

Oops - $dates will be an object of DOMNodeList.

You can then use the various methods to access the nodes and fetch the attributes.