Describe a situation where you had to optimize the performance of a PHP application. What strategies did you use?

To optimize a PHP application, I focus on several aspects. First, I analyze and optimize database queries, ensuring they are efficient and indexed properly. Caching mechanisms, both at the server and application levels, can significantly reduce response times. I also minimize HTTP requests and optimize images and other assets for faster loading. Profiling the code helps identify bottlenecks, allowing me to refactor or optimize specific functions. Additionally, using opcode caching tools like OPcache improves the performance of PHP scripts by reducing the need for redundant compilation.