On the Blackfire.io blog a new tutorial has been posted by Julien Pauli looking at some of the features of PHP 7 and how they relate to the overall performance in this latest major version of the language. In this first post in the series Julien talks about packed arrays.

This blog series will show you what changed inside the Zend engine between PHP 5 and PHP 7 and will detail how you, as a developer, may effectively use the new internal optimizations. We are taking PHP 5.6 as a comparison basis.

[...] Packed arrays is the first great PHP 7 optimization. Packed arrays consume less memory and are a bit faster in many operations than traditional arrays.

He gets into the specifics of how the packed arrays work, mentioning the internal optimization the language does, requiring no intervention in user-land code. He shows the difference between the PHP 5.6 performance and PHP 7 using the Blackfire.io tool - a difference of about a 70% gain.