如何从http.post (Angular2)调用的PHP文件中捕获回显的值？

import { HttpClient, HttpHeaders } from '@angular/common/http';

// ...

constructor(private http: HttpClient) {}

// ...

postData(data: any) {
  const url = 'http://example.com/api.php'; // PHP文件的URL地址
  const headers = new HttpHeaders().set('Content-Type', 'application/json');

  return this.http.post(url, data, { headers }).toPromise();
}

<?php
// ...

$data = $_POST; // 获取POST请求的数据

// 处理数据...

// 将处理结果返回给Angular2
echo json_encode($result);
?>

// ...

postData(data: any) {
  // ...

  return this.http.post(url, data, { headers }).toPromise()
    .then(response => {
      const result = response.json(); // 解析JSON格式的回显值
      console.log(result); // 打印回显值
    });
}