query only shapes with flag=1

[joerg p]

hello,

I have a country shapefile with a dbf file. The dbf file looks like this

country		flag
Australia	0
Botswana	0
Chile		1
Egypt		0
.
.
.

How do I get the shapes of the countries with flag=1?

At the moment I try:
$testlayer = $neuemap->map->getLayerByName("country_alle");
$testlayer->set( "filteritem", "cf" );
$testlayer->setFilter( "0" );
print_r($testlayer->queryByAttributes("cf", "0", MS_MULTIPLE));

But it doesn't work....

best regards
Joerg