Codeigniter/xml-rpc - How to customise the XML request format? - codeigniter

Question

I am new to Codeigniter, but I have been googling since the last 3 days but no chance.
Here is what the distant server is supposed to receive
Header content
(
[0] => Content-type: text/xml
[1] => Content-length: XXX
[2] => User-Agent: XXXXX/4.1/1.0
[3] => Authorization: Basic base64_encode("login:password");
)
<?xml version="1.0"?>
<methodCall>
<methodName>UpdateBalanceAndDate</methodName>
<params>
<param>
<value>
<struct>
<member>
<name>originNodeType</name>
<value>
<string>EXT</string>
</value>
</member>
<member>
<name>originHostName</name>
<value>
<string>XXXX</string>
</value>
</member>
<member>
<name>originTransactionID</name>
<value>
<string>XXXXXX</string>
</value>
</member>
<member>
<name>originTimeStamp</name>
<value>
<dateTime.iso8601>XXXXXXX</dateTime.iso8601>
</value>
</member>
<member>
<name>subscriberNumber</name>
<value>
<string>XXXXXXX</string>
</value>
</member>
<member>
<name>transactionCurrency</name>
<value>
<string>XOF</string>
</value>
</member>
<member>
<name>adjustmentAmountRelative</name>
<value>
<string>XXXXX</string>
</value>
</member>
<member>
<name>transactionCode</name>
<value>
<string>11</string>
</value>
</member>
<member>
<name>transactionType</name>
<value>
<string>XXXX</string>
</value>
</member>
</struct>
</value>
</param>
</params>
</methodCall>
<?xml version="1.0" encoding="utf-8"?>
And this is my code:
$this->load->library('xmlrpc');
$this->xmlrpc->server('server_ip_adress', 80);
$this->xmlrpc->method('UpdateBalanceAndDate');
$request = array('My Photoblog', 'http://www.my-site.com/photoblog/');
$request = array(
array(
array(
'originNodeType' => 'EXT',
'originHostName'=>'XXXX',
'originTransactionID'=>'XXXXXX',
'originTimeStamp'=>'XXXXXXX',
'transactionCurrency'=>'XOF',
'adjustmentAmountRelative'=>'XXXXX',
'transactionCode'=>'11',
'transactionType'=>'XXXX'
),
'struct'
)
);
$this->xmlrpc->request($request);
if ( ! $this->xmlrpc->send_request())
{
echo $this->xmlrpc->display_error();
}
Something is going wrong but I don't receive any error message from the server, I am checking the followings.
I need to customise the XML format of the request by adding a header
to the default XML format. Is this possible in Codeigniter? How?
Is there any function in Codeigniter (or generally in PHP) which
allows me to check the XML request before sending to the server?
(Something like var_dump() or print_r() ).
Thanks