What are the best practices for optimizing PHP code to improve performance and reduce unnecessary traffic time?

To optimize PHP code for improved performance and reduced unnecessary traffic time, it is essential to minimize database queries, use caching mechanisms, optimize loops and conditionals, and utilize efficient algorithms. Additionally, enabling opcode caching, using proper indexing in databases, and reducing file includes can also significantly enhance the performance of PHP applications.

// Example of optimizing PHP code by minimizing database queries
// Before optimization
$user = getUserById($userId);
$posts = getPostsByUserId($userId);
$comments = getCommentsByUserId($userId);

// After optimization
$user = getUserById($userId);
$posts = $user->posts;
$comments = $user->comments;