Hashtable collision resolution in PHP 7

Hi I'm trying to understand why PHP 7 hashtables are more efficient than PHP 5 hashtables. I'm confused about hashes that are in collision. In PHP 5 there were a linked lists to resolve collisions. What about PHP 7 ? Are there still linked lists ? I read somewhere that the solution taken in PHP 7 is L1 cache friendly so I conclude PHP 7 cannot resolve collisions using linked lists but rather arrays. If so please write me where the buckets that are in collision are stored in memory I mean by what field the array is pointed to by (e.g. zval.u2.next) and a few words of high level design of how it is implemented. thanks for help