ForbiddenChunk on "Count images from XML"

I am trying to run pull through an XML feed that shows the number of images relating to a property

console.log(type);
if (type == "buy"){
    var images = '. echo $images->count(); .';
} else{
    var images = 'No Images';
}

However I cannot get it to output right, can anyone help please?

Hope I've explained it right

I am expecting a number so if there are 5 images it will say 5 and I am currently getting . echo $images->count(); . which is just text, like it's unable to read it as PHP, when I try other ways I get undefined.