A good portion of PHP 7's performance improvements came from better structure packing:
https://wiki.php.net/phpng-int
http://nikic.github.io/2014/12/22/PHPs-new-hashtable-impleme...
https://wiki.php.net/phpng-int
http://nikic.github.io/2014/12/22/PHPs-new-hashtable-impleme...
Everyone likes to rag on PHP's chain, which is fair enough in some regards, but it has become a far better language recently, with more useful features, faster development cycles etc. People like nikic seem to be at the forefront of this.
Since PHP is a major part of my day job this all makes me very happy!