簡易なAPIライブラリ

api.js

<?php
namespace com\naosim\apilib;
use \Exception;

/**
* APIライブラリ
* 前提:
* - 1ファイル, 1APIで作成する
* - レスポンスはJSONとする (callbackがあればjsonp)
*/
class ApiUtil {
  function send($map) {
    $json = json_encode($map);
  // JSONの場合
    if(!isset($_GET['callback'])){
        header("Content-type: application/json");
        echo $json;
        return;
    }

    // JSONPの場合
    header("Content-type: application/javascript");
    $callback=$_GET['callback'];
    print <<<END
$callback($json);
END;
  }

  /**
  * Exception Handling
  */
  public function onException(Exception $e) {
      $this->send($this->failedMap($e->getMessage()));
  }

  /**
  * handle get call
  * if $action throw exception, then return error response
  * @var function $action
  */
  function get(Api $api) {
    try {
      $result = $api->invoke($this, new Request($_GET));
      if($result == null) return;
      $this->send($result);
    } catch(Exception $e) {
      $this->onException($e);
    }
  }

  /**
  * handle post call
  * if $action throw exception, then return error response
  * @var function $action
  */
  function post(Api $api) {
    try {
      $result = $api->invoke($this, new Request($_POST));
      if($result == null) return;
      $this->send($result);
    } catch(Exception $e) {
      $this->onException($e);
    }
  }

  function successMap(array $map) {
    return [
      'status' => 'success' ,
      'data' => $map
    ];
  }

  function failedMap(string $message) {
    return [
      'status' => 'failed', 
      'message' => $message
    ];
  }

  function getParamOrThrow(array $ary, string $key, Exception $exception) {
    if(isset($ary[$key])) {
      return $ary[$key];
    } else {
      throw $exception;
    }
  }

  /**
  * get value or throw
  * @throws Exception 
  */
  function required(array $ary, string $key) {
    return $this->getParamOrThrow($ary, $key, new Exception('required ' . $key));
  }

  /**
  * get value or default
  */
  function option(array $ary, string $key, $default) {
    return $ary[$key] ?? $default;
  }

  /**
  * call getValue() in value object.
  */
  function ValuePicker($targetObject) {
    /**
    * if value is hoge, then called like $targetObject->getHoge()->getValue().
    * if value is isFoo, then called like $targetObject->getIsHoge()->getValue().
    * @var $targetObject value name
    */
    return function ($key) use($targetObject) {
      // create getter method
      $methodName = 'get' . strtoupper(substr($key, 0, 1)) . substr($key, 1);
      // starts with 'is' & upper case after 'is'
      if(substr($key, 0, 2) === 'is' && ctype_upper(substr($key, 2, 1))) {
        $methodName = $key;
      }

      return $targetObject->$methodName()->getValue();
    };
  }
}// end API

function GET(Api $api) {
  (new ApiUtil())->get($api);
}

function POST(Api $api) {
  (new ApiUtil())->post($api);
}

class Request {
    private $params;
    public function __construct(array $params) {
        $this->params = $params;
    }

    public function getParams(): array {
        return $this->params;
    }

    public function option($key, $default) {
        return $this->params[$key] ?? $default;
    }

    public function required($key) {
        return $this->orThrow($key, new Exception('required ' . $key));
    }

    public function orThrow(string $key, Exception $exception) {
    if(isset($this->params[$key])) {
      return $this->params[$key];
    } else {
      throw $exception;
    }
  }
}

interface Api {
    function invoke(ApiUtil $apiUtil, Request $request): array;
}

ミニマムなサンプル

required_onceは適当に追加してください。

use function com\naosim\apilib\GET;
use com\naosim\apilib\Api;
use com\naosim\apilib\ApiUtil;
use com\naosim\apilib\Request;

class HogeApi implements Api {
    function invoke(ApiUtil $apiUtil, Request $request): array {
        $name = $request->required('name');
        $age = $request->required('age');

        return $apiUtil->successMap([
            'name' => $name,
            'age' => $age
        ]);
    }
}

GET(new HogeApi());

動作結果

成功

URL: http://localhost:8080/sample.php?name=mike&age=20

{
  "status": "success",
  "data": {
    "name": "mike",
    "age": "20"
  }
}

jsonpの場合
URL: http://localhost:8080/sample.php?name=mike&age=20&callback=foo

foo({"status":"success","data":{"name":"mike","age":"20"}}); 

失敗 (ageが足りない)

URL: http://localhost:8080/sample.php?name=mike

{
  "status": "failed",
  "message": "required age"
}

Api#invoke()の戻り値がそのままjsonで返る。
例外が発生した場合は、上記の失敗例と同じフォーマットで返る。
個人的にはerrorとdataが排他の関係になるとイイと思う。
例外時の返却をカスタマイズしたい場合は、ApiUtilを継承してonExceptionをオーバライドすればok。