gistfile1.php

<?php
function validate($data){
  $err = array();
  if(!array_key_exists('hoge', $data)){
    $err[] = 'error1';
  }
  if(!array_key_exists('piyo', $data)){
    $err[] = 'error2';
  }
  return $err;
}

function generate_data_from_internet_or_somewhere(){
  return isset($_GET)?$_GET:array();
}

function build_json_response($isSucceed, $data){
  $result = array(
  		'status' => $isSucceed,
  		'result' => $data
  	);
  return json_encode($result);
}

function build_responce($data){
  $error = validate($data);
  if(count($error) > 0){
    return build_json_response(false, $error[0]);
  }
  return build_json_response(true, $data);
}

$data = generate_data_from_internet_or_somewhere();
echo build_responce($data);
?>