gistfile1.php

<?php
function generate_data_from_internet_or_somewhere(){
  return isset($_GET)?$_GET:array();
}
function isError1($data){
  return !array_key_exists('hoge', $data);
}
function isError2($data){
  return !array_key_exists('piyo', $data);
}

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

function build_responce($data){
  if(isError1($data)){
    return build_json_response(false, 'error1');
  }
  if(isError2($data)){
    return build_json_response(false, 'error2');
  }
  return build_json_response(true, $data);
}

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