namespace foo {
    function testFunc($message) {
        echo 'foo testFunc with '.$message;
    }
}


namespace bar {
    function testFunc($message) {
        callMethod('foo','testFunc',$message);
    }
}

namespace {
    function callMethod($namespacename,$methodname,$arguments=NULL) {
        $nsFunc = '\\'.$namespacename.'\\'.$methodname;
        $nsFunc($arguments);
    }
    callMethod('bar','testFunc','Cool it work!!!');
}