What are some best practices for navigating file paths in PHP when accessing files in adjacent folders?

When accessing files in adjacent folders in PHP, it's important to use the correct file path to ensure that the files can be located and accessed successfully. One common approach is to use the `__DIR__` magic constant to get the current directory path and then construct the path to the desired file relative to that. Additionally, using the `DIRECTORY_SEPARATOR` constant can help ensure cross-platform compatibility when constructing file paths.

// Get the current directory path
$currentDirectory = __DIR__;

// Construct the path to the file in an adjacent folder
$filePath = $currentDirectory . DIRECTORY_SEPARATOR . 'foldername' . DIRECTORY_SEPARATOR . 'filename.txt';

// Access the file using the constructed path
$fileContents = file_get_contents($filePath);

// Output the contents of the file
echo $fileContents;