<?php

error_reporting(E_ALL);
$response = array();
ob_start();
// тут прверяем права доступа
$action = @$_GET['action'];
$filename = @$_GET['filename'];

switch ($action) {
    case 'read':
        if ( $data = file_get_contents($filename) ) {
            $response['data'] = $data;
        }

        break;

    case 'write':
        $append = @$_GET['append'];
        $lock = @$_GET['lock'];
        ( $data = file_get_contents('php://input') ) && file_put_contents( $filename, $data, ($append ? FILE_APPEND : 0) | ($lock ? LOCK_EX : 0) );
}

$response['error'] = ob_get_clean();
echo( json_encode($response) );

?>