Hi, I think I found an error at line 646 in MemModel.php:
function findVocabulary($vocabulary) {
...
if($this->indexed==0){
...
foreach($this->indexArr[5] as $key => $value){
...
}else{
...
foreach($this->triples as $value) {
This produces an error "Statement expected" in the MemModel add method when calling findVocabulary for a non-indexed model. It seems the line should read "if($this->indexed){" instead.