以下是一个使用Angular 9和HttpClient创建RESTful CRUD API的PHP版本的示例解决方案：

1. 首先，确保您已经安装了最新版本的Angular CLI和PHP。

2. 在终端或命令提示符中，使用以下命令创建一个新的Angular项目：

ng new angular-crud

3. 进入项目目录：

cd angular-crud

4. 创建一个名为api的文件夹，并在其中创建一个名为index.php的文件。这将是我们的PHP RESTful API的入口文件。

5. 在index.php中，添加以下代码：

connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

switch ($method) {
    case 'GET':
        $id = isset($_GET['id']) ? $_GET['id'] : null;
        if ($id) {
            $sql = "SELECT * FROM users WHERE id = " . $id;
        } else {
            $sql = "SELECT * FROM users";
        }
        $result = $conn->query($sql);
        if ($result->num_rows > 0) {
            $rows = array();
            while ($row = $result->fetch_assoc()) {
                $rows[] = $row;
            }
            echo json_encode($rows);
        } else {
            echo json_encode([]);
        }
        break;
    case 'POST':
        $name = $input['name'];
        $email = $input['email'];
        $sql = "INSERT INTO users (name, email) VALUES ('$name', '$email')";
        if ($conn->query($sql) === TRUE) {
            echo json_encode(array('message' => 'User created successfully'));
        } else {
            echo json_encode(array('error' => 'Error creating user'));
        }
        break;
    case 'PUT':
        $id = $request[0];
        $name = $input['name'];
        $email = $input['email'];
        $sql = "UPDATE users SET name = '$name', email = '$email' WHERE id = $id";
        if ($conn->query($sql) === TRUE) {
            echo json_encode(array('message' => 'User updated successfully'));
        } else {
            echo json_encode(array('error' => 'Error updating user'));
        }
        break;
    case 'DELETE':
        $id = $request[0];
        $sql = "DELETE FROM users WHERE id = $id";
        if ($conn->query($sql) === TRUE) {
            echo json_encode(array('message' => 'User deleted successfully'));
        } else {
            echo json_encode(array('error' => 'Error deleting user'));
        }
        break;
}

$conn->close();

?>

6. 在终端或命令提示符中，使用以下命令将index.php文件复制到Angular项目的根目录中：

cp api/index.php .

7. 打开src/app/app.module.ts文件，并添加以下代码：

import { HttpClientModule } from '@angular/common/http';

@NgModule({
  // ...
  imports: [
    // ...
    HttpClientModule
  ],
  // ...
})
export class AppModule { }

8. 打开src/app/app.component.ts文件，并添加以下代码：

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

export class AppComponent implements OnInit {
  users: any[] = [];

  constructor(private http: HttpClient) {}

  ngOnInit() {
    this.getUsers();
  }

  getUsers() {
    this.http.get('http://localhost/api').subscribe(
      response => {
        this.users = response;
      },
      error => {
        console.log(error);
      }
    );
  }

  createUser(user: any) {
    this.http.post('http://localhost/api', user).subscribe(
      response => {
        console.log(response);
        this.getUsers();
      },
      error =>