I'm seeking an experienced developer to migrate a web application from PHP 5.x to PHP 8.1. Requirements: - Upgrade codebase for compatibility with PHP 8.1. - Ensure application functionality remains intact post-migration. - Optimize performance and security during the upgrade. Ideal Skills: - Extensive experience with PHP, especially legacy versions. - Strong understanding of PHP 8.1 features and changes. - Proven track record in migrating large web applications. - Familiarity with testing and debugging in PHP. Please provide examples of similar work done.