PHP get contents of files and directories

<?php
$filename = $_SERVER['DOCUMENT_ROOT'] . "/sites/default/settings.php";
$file = file_get_contents($filename);
if (is_writable($filename)) {
    echo "The file is writable<br />\n";
} else {
    echo "The file is not writable<br />\n";
}
print "<pre>";
print_r($file);
print "</pre>";
 
/**
 * list all directories/folders in a specified location
 **/
//path to directory to scan
$directory = $_SERVER['DOCUMENT_ROOT'] . "/directory/";
 
//get all files in specified directory
$files = glob($directory . "*");
 
//print each folder name
foreach($files as $file)
{
 //check to see if the file is a folder/directory
 if(is_dir($file))
 {
  echo $file;
 }
}
 
/**
 * list all image files in a specified location
 **/
//path to directory to scan
$directory = $_SERVER['DOCUMENT_ROOT'] . "/sites/all/modules/custom/otmobile_meter_registration/includes/submissions/";
 
//get all image files with a .jpg extension.
// $files = glob($directory . "*.jpg");
//get all files regardless of extension
$files = glob($directory . "*");
 
//print each file name
foreach($files as $files)
{
echo $image;
}
?>