The document compares the performance of HHVM and different PHP versions in running Drupal 7 and Drupal 8 benchmark tests. It finds that for Drupal 7, HHVM performs best but PHP 5.4 with APC is also recommended. For Drupal 8, HHVM performs best but PHP 5.5 with opcode caching is recommended if HHVM cannot be used. The benchmarks were run on Ubuntu 14.04 with 2 vCPU and 2GB RAM.