What is the best way to read files from a directory in PHP, considering security implications and access restrictions?

When reading files from a directory in PHP, it is important to consider security implications and access restrictions to prevent unauthorized access to sensitive files. One way to achieve this is by using the `scandir` function to retrieve a list of files in a directory, then validating each file before reading its contents. Additionally, you can set up proper file permissions on the directory to restrict access.

$directory = '/path/to/directory/';

if (is_dir($directory)) {
    $files = scandir($directory);
    
    foreach ($files as $file) {
        if ($file !== '.' && $file !== '..') {
            // Validate file here before reading its contents
            $filePath = $directory . $file;
            $fileContent = file_get_contents($filePath);
            // Process file content
        }
    }
} else {
    echo "Invalid directory";
}