Downgrading PHP code allows developers to use the latest PHP features while maintaining compatibility with older environments, a process facilitated by tools like Rector and Phabel. While Rector is a versatile tool that can modify PHP code in multiple ways, including modernization and quality improvement, Phabel focuses solely on downgrading PHP code. Rector is run on servers and offers more control and reliability, making it suitable for production environments, whereas Phabel operates on the client side, simplifying integration but potentially leading to issues during execution, such as increased processing time and the need for manual fixes. Both tools have unique strengths, but Rector's extensive community support and flexibility make it more dependable for comprehensive code transformation tasks. Despite Phabel's limitations, its integration with Composer and its potential for future development make it a promising tool for specific downgrading needs.