Seemingly random SoapFault: not a valid method

Question

I'm experiencing a problem with my SOAP solution. Sometimes I get an error saying the following:

Function (functionA) is not a valid method for this service

Edit 8 months later Although I could not find the cause of the problem I was able to work around it. Whenever I recieve an response from the API I check for the SoapFault and just send another identical request and use the answer that comes back the second time.(posted as an answer)

This occurs in calls from PHP like:

functionA() - expected response
functionA() - expected response
functionA() - SoapFault
functionA() - expected response

Same result is to be expected in all the above calls and the same parameters are used(if any). Since it's working fine for almost all calls I know that the function and the corresponding WSDL is there.

What I thougt were the problem was caching an old version which would not have that function. I tried disabling the caching with:

ini_set("soap.wsdl_cache_enabled", "0");

And makeing every call with added with a random dummy parameter as well as disabling it when I use Zend_SoapClient.

'cache_wsdl' = false

I hope someone could point me in any direction or have any direct suggestion on what could be the cause.

My code looks like:

public function __construct()
{
        $wsdl =  "http://catlovers.nl/index.php?wsdl&dummy=".rand(1000,9999);

        $this->_client = new Zend_Soap_Client($wsdl, array(
            'soapVersion' => SOAP_1_1,
            'cache_wsdl' => false 

        ));
        $this->_client->setWsdlCache(false);
}

function __call($name, $arguments) // Calls are made this way
{
    array_unshift($arguments, $this->_apiKey, $this->_user, $this->_password);
    return call_user_func_array(array($this->_client, $name), $arguments);
}
public function getCat()
{
    return ($this->__call('getCat',array()));
}

On "the other side" I have:

$server = new nusoap_server();

$server->wsdl->addComplexType('Cat', ....

$server->register( 'getCat', return Cat ...

function getCat($apikey, $email, $password)
{
  $cat = $db->get("redCat");
  return $cat;
}

Answer 1

So the problem was still there after trying other solutions so I was never able to find underlying cause of the problem. On the other hand I found a way to work around the problem that has been working since I wrote it. This is how my call to the API looks like with user,password and key for authentication.

function __call($name, $arguments)
{
    /* Using the stored data to ensure that the user is allowed to access */
    /* ............... */

    array_unshift($arguments, $this->_apiKey, $this->_user, $this->_password);
    $call = call_user_func_array(array($this->_client, $name), $arguments);
    if(isset($call->faultstring) && substr(trim($call->faultstring),0,7) == "Function")
    {
        $recall = call_user_func_array(array($this->_client, $name), $arguments);
        return $recall;
    }
    else
        return $call;
}

This is basicly: if it doesn't work the first time just try again.