The server handles headers much like it handles other types of calls. You set up a class to handle the headers and register it just as you would a regular server object. The way the server knows to pass headers to the header class is by the namespace given to the class.

Server that handles headers

<?php
require_once 'SOAP/Server.php';

class Header_Handler {
    var $method_namespace = 'urn:Header_Handler';
    var $authenticated = FALSE;
    
    function authenticate($authinfo)
    {
        if ($authinfo->username == 'foo' &&
            $authinfo->password == 'bar') {
            $this->authenticated = TRUE;
            return 'Authentication OK';
        }
        $faultcode = 'Client';
        $faultstring = 'Invalid Authentication';
        $faultactor = $this->method_namespace;
        $detail = NULL;
        return new SOAP_Fault($faultstring,
                              $faultcode,
                              $faultactor,
                              $detail);
    }
}

class Simple_Server {
    var $method_namespace = 'urn:Simple_Server';
    
    function Simple_Server() {
        global $server;
        $this->headers = new Header_Handler();
        $server->addObjectMap($this->headers);
    }
    
    function echoString($text) {
        if (!$this->headers->authenticated) {
            $faultcode = 'Client';
            $faultstring = 'You must send authentication headers';
            $faultactor = $this->method_namespace;
            $detail = NULL;
            return new SOAP_Fault($faultstring,
                                  $faultcode,
                                  $faultactor,
                                  $this);
        }
        return $text;
    }
}

$server = new SOAP_Server;
$myserver = new Simple_Server();
$server->addObjectMap($myserver);
$server->service($HTTP_RAW_POST_DATA);
?>
Client sending headers

<?php
require_once 'SOAP/Client.php';

$soapclient = new SOAP_Client('http://localhost/talk/server3.php');

$header = new SOAP_Header(
        '{urn:Header_Handler}authenticate',
        'Struct',
        array('username'=>'foo','password'=>'bar'),
        1);

$soapclient->addHeader($header);

$ret = $soapclient->call('echoString',
                         array('inputString'=>'test'),
                         'urn:Simple_Server');
?>
The SOAP Wire
OUTGOING:

POST /talk/server3.php HTTP/1.0
User-Agent: PEAR-SOAP 0.6.1
Host: localhost
Content-Type: text/xml; charset=UTF-8
Content-Length: 834
SOAPAction: ""

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

<SOAP-ENV:Envelope
 xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
 xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
 xmlns:ns4="urn:Header_Handler"
 xmlns:ns5="urn:Simple_Server"
 SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">

<SOAP-ENV:Header>
<ns4:authenticate
  SOAP-ENV:actor="http://schemas.xmlsoap.org/soap/actor/next"
  SOAP-ENV:mustUnderstand="1">
    <username xsi:type="xsd:string">foo</username>
    <password xsi:type="xsd:string">bar</password>
</ns4:authenticate>
</SOAP-ENV:Header>

<SOAP-ENV:Body>
<ns5:echoString>
<inputString xsi:type="xsd:string">test</inputString>
</ns5:echoString>
</SOAP-ENV:Body>

</SOAP-ENV:Envelope>


INCOMING

HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Date: Wed, 26 Jun 2002 06:54:40 GMT
X-Powered-By: PHP/4.2.1
Server: PEAR-SOAP 0.6.1
Content-Type: text/xml; charset=UTF-8
Content-Length: 695

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

<SOAP-ENV:Envelope
 xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
 xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
 xmlns:ns4="urn:Header_Handler"
 xmlns:ns5="urn:Simple_Server"
 SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">

<SOAP-ENV:Header>
<ns4:authenticate xsi:type="xsd:string">
         Authentication OK
</ns4:authenticate>
</SOAP-ENV:Header>

<SOAP-ENV:Body>
<ns5:echoStringResponse>
<return xsi:type="xsd:string">test</return>
</ns5:echoStringResponse>
</SOAP-ENV:Body>

</SOAP-ENV:Envelope>