PHP Soap Issue

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server.php:
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<?php
class TestClass {
  public function importData($data)
  {
    $fd = fopen("testsoap.log", "a");
    fwrite($fd, var_export($data, true));
    fclose($fd);

    return array();
  }
}

$server = new SoapServer("test.wsdl");
$server->setClass("TestClass");
$server->handle();


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client.php:
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<?php
for($i = 1; $i < 40000; $i++) {
  $data .= "+";
}

$obj = new stdClass();
$obj->someVariable = $data;
$client = new SoapClient("test.wsdl");
$something = $client->importData($obj);
var_dump($something);

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WSDL:
----------------------------------------------
<definitions name="importData"
  targetNamespace="http://some_url"
  xmlns:es="http://url_to/server.php"
  xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
  xmlns="http://schemas.xmlsoap.org/wsdl/"
>

  <message name="importDataRequest">
    <part name="irgendwas" element="xsd:string"/>
  </message>

  <portType name="importDataPortType">
    <operation name="importData">
      <input message="es:importDataRequest"/>
    </operation>
  </portType>

  <binding name="importDataSoapBinding"
           type="es:importDataPortType">
    <soap:binding style="document"
                  transport="http://schemas.xmlsoap.org/soap/http"/>
    <operation name="importData">
      <soap:operation
        soapAction="http://url_to/server.php"/>
      <input>
        <soap:body use="literal"
          namespace="http://some_url"/>
      </input>
    </operation>
  </binding>

  <service name="importDataService">
    <documentation>import Data</documentation>
    <port name="importDataPort"
          binding="es:importDataSoapBinding">
      <soap:address location="http://url_to/server.php"/>
    </port>
  </service>

</definitions>