Most improvements in PHP 5.6.x have no impact on existing code. There are a few incompatibilities and new features that should be considered, and code should be tested before switching PHP versions in production environments.
Ayrıca, şu PHP sürümleri arasında geçiş kılavuzlarına da bakınız: 5.0.x, 5.1.x, 5.2.x, 5.3.x, 5.4.x and 5.5.x.