Official PHP 7.3 Migration Guide

My favorite features in this release:

* Trailing commas in function/method calls

* array_push() and array_unshift() can now be called with a single argument (helpful when using the spread operator)

* TypeError now reports wrong types as int and bool instead of integer and boolean (no more "Argument must be an instance of integer, integer given" errors)

* Deprecation of case-insensitive constants

* json_decode() and json_encode() now support a JSON_THROW_ON_ERROR flag (removing the need to call json_last_error() to see if an error occurred)

* setcookie() now accepts an associative array of options, and supports the samesite attribute

* More flexible heredoc syntax