title: Angularjs 500 (Internal Server Error) in a very basic program
body: <p>Hello I have a very basic program that throws the error ¿can you tell why?</p>
  
  <p>the php: Basically puts into a file the post that is a JSON.
  It's a part of a long polling system.</p>
  
  <pre><code>&lt;?php
  if( empty($_POST || !isset($_POST)) ) {
      $last_ajax = null;
  } else {
      $last_ajax = time();
  }
  clearstatcache();
  $last_change = filemtime('cache.txt');
  
  if ($last_ajax == null || $last_change &gt; $last_ajax) {
  
      // Load the ajax
      $R = json_decode(file_get_contents('php://input'), true);
      // Load into memory the file
      $F = json_decode(file_get_contents('cache.txt'), true);
      // If not empty the file append
      if(!empty($F)) {
          $S = array_merge_recursive($F, $R);
          file_put_contents('cache.txt', json_encode($S), true); 
      // Else just write into the file the post
      } else {
          file_put_contents('cache.txt', json_encode($R), true); 
      }
      echo json_encode(file_get_contents('cache.txt'), true);
      break;
  }
  ?&gt;
  </code></pre>
  
  <p>And the very simple post in Angular.
  It's just a simple post that sends to de php above the data, that is a JSON</p>
  
  <pre><code>    var enrol = angular.module("enrol",[]);
  
  enrol.controller("enrolController", function($scope, $http){
  
      $scope.submit  = function() {
          console.log("Submitting");
          $http({
              method  : "POST",
              url     : "dependencies/cache.php",
              data    : {
                  'action': 'enrol',
                  'data': {
                      'Login': $scope.apliclogin,
                      'Password': $scope.aplicpass,
                      'rol': {
                          'admin': $scope.admin,
                          'sala': $scope.sala,
                          'barra': $scope.barra,
                          'cocina': $scope.cocina,
                          'caja': $scope.caja
                      }
                  }
              },
              headers : { 'Content-Type': 'application/x-www-form-urlencoded' }
          }).success(function(data){
              console.log(data);
          });
      };
  });
  </code></pre>