php静态网站上没有使用NGINX指定输入（Homestead问题？）

I have a set of apps for development on a server that uses nginx and all of them work except for one website that says "No input file specified" whenever I load it from the index.php (it reaches the login page located at app/login.php. There aren't dynamically generated web pages.

nginx.conf

server {
listen 80;
server_name farmacia.app;
root /vagrant/farmacia/elmuertosano/;

location / {
index index.php;
try_files $uri $uri/ =404;
}

location ~ \.php$ {
fastcgi_split_path_info ^(.\+.php)(/.+)$;
fastcgi_pass unix:/var/run/php/php7.1-fpm.sock;
fastcgi_index index.php;
include fastcgi_params;
}

}

index.php

<?php
    session_start();
    if(!isset($_SESSION['usuario']) |! $_SESSION['usuario']){
        header('Status: 301 Moved Permanently', false, 301);
        header('Location:/elmuertosano/app/login.php');
        exit();
    } else {
        header('Status: 301 Moved Permanently', false, 301);
        header('Location:/elmuertosano/app/inicio.php');
        exit();
    }
?>

app/login.php

<?php
require_once '../libsigma/Sigma.php';


$plantilla = &new HTML_Template_Sigma('../plantilla/');
$plantilla -> loadTemplateFile('inicio.tlp.html');

$titulo_pagina = 'Iniciar Sesión';

$contenido1 = '<p><img src="../plantilla/img/logo-farmacia1.gif" alt="farmacia"></p>
    <fieldset>
                            <legend>
                                Iniciar Sesión
                            </legend>
<form method="post" class="pure-form pure-form-stacked" action="../operadores/autentificar.php">
<label for="correo">Correo</label><input type="text" name="authcorreo" id="authcorreo">
<label for="contraseña">Contraseña</label><input type="password" name="authpassword" id="authpassword">
<input type="submit" value="Ingresar">
</fieldset>
</form>




<br/>

';

$plantilla -> setVariable('titulo_pagina', $titulo_pagina);
$plantilla -> setVariable('contenido1', $contenido1);
$plantilla -> parse();
$plantilla -> show();
?>

EDIT: I've used the php server and it throws a "TOO MANY REDiRECTS" error. Perhaps a session problem? I already gave sessions folder 777 permissions.

EDIT: I've noticed that the problem probably has relation to Homestead which is the vagrant machine I'm using. It has got a session management problem. Even tweaking its php.ini doesn't seem to work well. On XAMPP it works. I'll leave open this question so if somebody knows how to fix the session problem on Homestead. This didn't work.