Since PHPStan 2.0 we start to narrow PHP version related information for more precise results.

Markus Staab

PHPStan 2.0 introduces dead code detection for PHP version checks by narrowing type information based on composer.json requirements or NEON config settings. The feature identifies always-true or always-false conditions in PHP_VERSION_ID, PHP_MAJOR_VERSION, and version_compare() calls, helping developers remove obsolete code for unsupported PHP versions. The implementation uses declared PHP version ranges to detect unreachable branches in version-specific logic and tests.

Dead code detection for PHP_* constants