How do I scan a directory and list the folders, file name, and contents of files in json format?

{
    "file1": "file1 contents",
    "file2": "file2 contents",
    "ThisIsAFolder": {
        "fileInsideFolder": "folder contents"
        "fileInsideFolder2": "folder contents"
    }
}

<?php
//this file is for aOS

//this gets your files in the directory (Insert starting directory here)
$main = "message_standalone";

$iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($main));
$allFiles = array_filter(iterator_to_array($iterator), function($file) {
    return $file->isFile();
});

$filenames = array_keys($allFiles);

//print_r($filenames);

//$filearray=array();

foreach($filenames as $filename){

$filenamens=trim(substr($filename, strpos($filename, '\\') + 1));

$filearray[$filenamens]=htmlentities(file_get_contents($filename));

}

$json=json_encode($filearray, JSON_PRETTY_PRINT);

echo "<pre>";
print_r($json);
echo "<//pre>";

?>