The Blackfire.io blog has just wrapped up their series of posts covering some of the performance improvements that came along with PHP 7. In each post of the series they get into detail on one area, sharing some brief code samples and screenshots from the service showing the performance different between PHP 7 and PHP 5.

Julien Pauli, PHP contributor and release manager, details what changed between PHP 5 and PHP 7, and how to migrate and make effective use of the language optimizations. All statements are documented with specific examples and Blackfire profiles.

The topics covered are:

• Packed arrays
• How ints and floats are freed PHP 7
• Encapsed strings optimization
• References mismatch
• Immutable arrays

While some of the examples are (sort of) Symfony related, they're mostly about generic language level features and include some other considerations to think about when using the feature and the performance impact on your application.