arrays - PHP Error : Can't use function return value in write context

Can't seem to see what's the problem in this one,
Should be simple but i seem to be witless.

    if(empty(search($class,'id',$p_cid))){
     unset($categories[$elementKey]);
 }

search function returns an array.

Answer

It should be this way:

$arr = search($class, 'id', $p_cid);
if (empty($arr)) {
    unset($categories[$elementKey]);
}