In terms of best practices, what considerations should be made when handling file paths in PHP to ensure compatibility across different systems?

When handling file paths in PHP to ensure compatibility across different systems, it's important to use PHP's built-in functions like `DIRECTORY_SEPARATOR` and `realpath()` to handle file paths dynamically. Additionally, using the `__DIR__` magic constant can help create absolute paths in a platform-independent way.

// Example of handling file paths in a platform-independent way
$filePath = __DIR__ . DIRECTORY_SEPARATOR . 'files' . DIRECTORY_SEPARATOR . 'example.txt';
$realPath = realpath($filePath);

if ($realPath) {
    // File path is valid
    echo "File path: $realPath";
} else {
    // File path is invalid
    echo "Invalid file path";
}