How can the PHP script be optimized to improve performance and prevent potential vulnerabilities, such as directory traversal attacks?

To optimize the PHP script and prevent directory traversal attacks, it is important to sanitize user input and validate file paths before accessing or including them in the script. This can be done by using functions like realpath() to resolve the full path of a file and ensure it is within the expected directory structure. Additionally, implementing proper input validation and using secure file handling functions can help improve performance and prevent vulnerabilities.

// Sanitize and validate file path before accessing it
$basePath = '/path/to/secure/directory/';
$filePath = realpath($basePath . $_GET['file']);

if (strpos($filePath, $basePath) !== 0) {
    die('Invalid file path');
}

// Proceed with file handling operations
$fileContents = file_get_contents($filePath);
echo $fileContents;