How to interact with the Tessitura web API via GET in PHP

Some web API functions will inexplicably fail when called from a standard PHP SOAP client. Here's a workaround: A function that calls a web API method via GET. Please note that this may not be sufficiently secure for sending sensitive information such as passwords, and I haven't tested it thoroughly on a wide variety of API methods, so use it at your own risk ;-)

protected function callTessituraViaGet($functionName,$parameters)
{
    // If you store the Tessitura WSDL location in a separate configuration file,
    // you may need to strip the query from the full WSDL URL.

    $tessituraURLComponents = explode('?',TESSITURA_WSDL_LOCATION);
    $URLToTessituraASPX = $tessituraURLComponents[0];

    // Build the GET query string for the Tessitura call

    $queryString = "/$functionName?";
    foreach($parameters as $key => $value)
        $queryString .= urlencode($key) . '=' . urlencode($value) . '&';

    // Replace die() with your own function to handle connection failure
    $handle = fopen($URLToTessituraASPX . $queryString, 'r')
              or die("Can't connect to Tessitura.");

    $response = '';
    while(!feof($handle))
        $response .= fgets($handle);

    // Convert response to SimpleXMLElement
    $response = new SimpleXMLElement($response);
    $response = $response->children('urn:schemas-microsoft-com:xml-diffgram-v1');
    $response = $response->children('');
    $response = $response->children();
    return $response;
}

And here's an example of this function in use:

$performances = $this->callTessituraViaGet('GetPerformancesEx3', array(
            'sWebSessionId'          => $_SESSION['tessSessionKey'],
            'sStartDate'             => date('n-j-Y',$this->startTimestamp),
            'sEndDate'               => date('n-j-Y',$this->endTimestamp),
            'iVenueID'               => -1,
            'iModeOfSale'            => 6,
            'iBusinessUnit'          => 1,
            'sSortString'            => '',
            'sKeywords'              => '',
            'cKeywordAndOrStatement' => '',
            'sArtistLastName'        => '',
            'sFullText'              => '',
            'sFullTextType'          => '',
            'sContentType'           => '',
            'sPerformanceIds'        => '',
            'sSeasonIds'             => '' ));