PHP Extension 5.9.0 released

• Notice: Active development for PHP 7.0 and 7.1 has been discontinued. While new features will only be available for PHP 7.2+, our future releases will continue to ship with support for PHP 7.0 and 7.1 with the current feature set.
• Improvement: Various internal refactoring have been performed, improving debuggability, performance and reducing memory usage.
• Bugfix: Fix instrumentation of rdkafka’s poll() and flush() functions when internal functions are instrumented with the observer API.
• Bugfix: Fix memory leak during sending of PHP Info when tideways.features.stats is active.