What are the potential pitfalls of using include and require in PHP for outsourcing code?

One potential pitfall of using include and require in PHP for outsourcing code is the risk of including a file multiple times, which can lead to redeclaration of functions or variables and cause errors in your code. To solve this issue, you can use include_once or require_once instead, which will ensure that the file is only included once.

// Use include_once or require_once to prevent multiple inclusions of the same file
include_once 'file.php';