What are the differences in PHP syntax between Windows and Linux systems?

When writing PHP code that needs to be compatible with both Windows and Linux systems, it's important to be aware of the differences in file paths. Windows systems use backslashes (\) in file paths, while Linux systems use forward slashes (/). To ensure cross-platform compatibility, it's best to use the DIRECTORY_SEPARATOR constant, which will automatically use the correct slash for the current operating system.

// Use DIRECTORY_SEPARATOR constant for cross-platform compatibility
$file_path = 'path' . DIRECTORY_SEPARATOR . 'to' . DIRECTORY_SEPARATOR . 'file.php';
include $file_path;