Parameter Missing in XML String - php

Question

I am passing an xml string to https://insurance-api.pingtree.co.uk/api through curl but is getting parameter error in response (code 12 0) which can be also seen if you browse the above mentioned url.The parameter is defined in the xml i.e. the campaign code then why isn't the system recognizing it. here is my code below which i also got from the http://www.quinternet.com site.
<?php
/**
* Initialize the request xml string here.
* The string in the tag like '[int]' should be replaced with actual value.
* The string in the square brackets is the data type.
*/
$request_string =
'<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope
xmlns:xsi="http://www.w3.org/2001/XMLSchemainstance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:urn="urn:pt_service">
<soapenv:Header />
<soapenv:Body>
<urn:submit
soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<campaign_code>dllfYg0JBwQ</campaign_code>
<site_url>www.surelifecover.co.uk</site_url>
<client_ip>127.0.0.1</client_ip>
<policy_type>J</policy_type>
<cover_purpose>1</cover_purpose>
<cover_amount>50000</cover_amount>
<cover_term>1</cover_term>
<title>1</title>
<first_name>INTRODUCERTEST</first_name>
<last_name>wwww</last_name>
<dob >1995-04-05</dob >
<email>will#bitscube.com</email>
<home_phone>07111111111</home_phone>
<best_call_time>1</best_call_time>
<gender>F</gender>
<is_smoker>Y</is_smoker>
<title2>1</title2>
<first_name2>ww</first_name2>
<last_name2>wwww</last_name2>
<dob2>1991-02-03</dob2>
<email2>913661383#qq.com</email2>
<home_phone2>07111111112</home_phone2>
<best_call_time2>2</best_call_time2>
<gender2>M</gender2>
<is_smoker2>N</is_smoker2>
<terms_consent>Y</terms_consent>
<privacy_content>Y</privacy_consent>
<mode>LIVE</mode>
<keyword>life ins</keyword>
<match_type>1</match_type>
<network>ABC</network>
<device>mobile</device>
<ref>00</ref>
<v1>var1</v1>
<v2>var2</v2>
<v3>var3</v3>
<v4>var4</v4>
<v5>var5</v5>
<i1>1</i1>
<i2>2</i2>
<i3>3</i3>
<i4>4</i4>
<i5>5</i5>
</urn:submit>
</soapenv:Body>
</soapenv:Envelope>
</env:Envelope>';
echo htmlspecialchars($request_string);
echo '<br>';
/**
* The values of the following fields please refer
*to the reference field list spec*
//setup the request headers here, notice at the action string and SOAPAction string */
$request_headers = array('Content-Type: application/soap+xml;charset=utf-8;action="urn:pt_service#Webservice#submit"',
'SOAPAction: "urn:pt_service#Webservice#submit"',
'Content-length: '.strlen($request_string) );
//setup the service url here
$service_url = 'https://insurance-api.pingtree.co.uk/api';
//setup the user agent for the request
$user_agent = $_SERVER['HTTP_USER_AGENT'];
//initialize the curl here
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $service_url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLINFO_HEADER_OUT, FALSE );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE );
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE );
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
curl_setopt($ch, CURLOPT_POST,TRUE );
curl_setopt($ch, CURLOPT_VERBOSE, TRUE);
curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
curl_setopt($ch, CURLOPT_POSTFIELDS,$request_string);
curl_setopt($ch, CURLOPT_HTTPHEADER,$request_headers);
//do the submit process here
$result= curl_exec ($ch);
$response_string = curl_exec($ch);
// Convert API feed to xml object
var_dump($response_string);
$xml = simplexml_load_string($response_string);
$name = $xml->response->status;
echo $name;
//-----------------------------------------------
//parsing the response string here
/*example response below. Please get detail
refer for the reponse in specs.
<?xml version="1.0" encoding="UTF8"?>
<response>
<result>20</result>
<status>1</status>
<commission>10.00</commission>
<reference>347</reference>
<message><![CDATA[Accepted]]></message>
<redirect_url>
http://insurance-api.pingtree.co.uk/redirect?p=bUzbir4VhB-BB-Z_gMxVSy8YT15gxUB9iJMBGxi_aOq5PQuDBf_JPqgvc2egv6orCj6TJkeR5g6tX1y0D7hZgbV6DdBAlzbccKmkFNG4-PgWmaNR9LQ57cUQg6jTOXuB
</redirect_url>
</response>
//-----------------------------------------------*/
curl_close($ch);
?>