server does not return data that I send with angular2

the component code

 onSubmit(form){ 
    var success = false;
    var error = false;

    this.http.post('http://localhost/api/', 
    JSON.stringify(form.value))
    .map(res => res)
    .subscribe(dados => console.log(dados));

  }

the php server code

if(!isset($_POST)):
    ResultJson(['erro'=> true, 'messagem'=> 'nenhum dado foi informado']);
else:
    var_dump($_POSt);
endif;

the problem is that it returns an empty array already tried in several ways and I can not solve anyone can help me? thank you for the strength of you