PHP 5.6

PHP 5.6 is a release of the PHP language shipped in August 2014, the last in the 5.x branch. It closed out more than a decade of development on the Zend Engine 2 and, for years, was the minimum requirement of many popular applications, including older versions of WordPress.

Why PHP 5.6 mattered

PHP 5.6 introduced tidying syntax improvements along with security fixes:

• constant expressions — the ability to define constants based on simple calculations;
• the argument-unpacking operator (...) — passing an array as a list of function arguments;
• the exponentiation operator (**) — a cleaner way to write powers than the pow function;
• improved large-file uploads and better session management.

Although the changes were less revolutionary than in PHP 5.3, version 5.6 was stable and widely supported, making it a safe starting point before the leap to PHP 7.

Practical applications

Security support for PHP 5.6 ended at the close of 2018, and it was the last release in the 5.x series. Using it in production today is dangerous — it receives no patches. Because many sites ran on 5.6 for years, its retirement forced administrators into a mass migration to PHP 7.0, which offered roughly double the performance. Modern hosting and VPS servers provide only supported releases, so keeping an old site running requires updating the code to one of the current PHP branches.

A symbolic end of an era

Retiring PHP 5.6 was symbolic — it closed out the entire 5.x series, which had defined what programming in the language looked like for over a decade. For many teams it was an opportunity not just to change the version number but to thoroughly review and modernise ageing code. Moving to the 7 series was often combined with refactoring, introducing type declarations and tidying up dependencies, which resulted in faster, more maintainable applications.