Im trying to produce a request that looks like this.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.ws.vgregion.se/">
<soapenv:Header/>
<soapenv:Body>
<ser:searchPerson>
<ser:arg0>(cn=togus)</ser:arg0>
<ser:arg1>
<ser:string></ser:string>
</ser:arg1>
<ser:arg2>KIV</ser:arg2>
<ser:arg3>o=VGR</ser:arg3>
<ser:arg4>2</ser:arg4>
</ser:searchPerson>
</soapenv:Body>
</soapenv:Envelope>

when I try something like this
$client->call('searchPerson', array('ser:arg0' => '(cn=togus)','ser:arg1'=>"" ....
I get parse error from server.
when i send the envelope above like $client->send($msg), it works

How do i create the exact request like the one above?