AngularJS $http.post response determine ERROR
<p>I'm using AngularJS $http.post to call PHP in my login-function. The PHP gives back a token and if not exists the word "ERROR".
<br>PHP-Code:</p>

<pre><code>....
echo json_encode($token);
} else {
echo "ERROR";
} 
</code></pre>

<p><br> Controller.js:</p>

<pre><code>   var request = $http({
   method: "post",
   url: constantService.url + 'login.php',
   data,
   headers: {
       'Content-Type': 'application/x-www-form-urlencoded'
   }
   });

 request.success(function(response) {

   $localstorage.set("token", JSON.stringify(response));

   var showAlert = function() {
       var alertPopup = $ionicPopup.alert({
           title: ' successful token-based login',
           template: response
       });
       alertPopup.then(function(res) {
           console.log(res);
           $state.go('home');
       });
   };
   showAlert();

  });

 request.error(function(data, status, headers, config) {

   console.log('An error occurred ');

   var showAlert = function() {
       var alertPopup = $ionicPopup.alert({
           title: 'Error',
           template: 'check your login credentials'
         });
         alertPopup.then(function(res) {
         });
      };
      showAlert();
    });
</code></pre>

<p>When i get back a correct token it's working without problems. When i get back the word "ERROR" ( no token exists ) i get the following error in chrome inspector:</p>

<pre><code>**SyntaxError: Unexpected token E**
at Object.parse (native)
at fromJson       (http://localhost:8100/lib/ionic/js/ionic.bundle.js:9764:14)
at defaultHttpResponseTransform (http://localhost:8100/lib/ionic/js/ionic.bundle.js:17278:16)
at http://localhost:8100/lib/ionic/js/ionic.bundle.js:17363:12
at forEach (http://localhost:8100/lib/ionic/js/ionic.bundle.js:9022:20)
at transformData (http://localhost:8100/lib/ionic/js/ionic.bundle.js:17362:3)
at transformResponse (http://localhost:8100/lib/ionic/js/ionic.bundle.js:18088:23)
at processQueue (http://localhost:8100/lib/ionic/js/ionic.bundle.js:21888:27)
at http://localhost:8100/lib/ionic/js/ionic.bundle.js:21904:27
at Scope.$eval (http://localhost:8100/lib/ionic/js/ionic.bundle.js:23100:28)
</code></pre>

<p>Whats the correct way to give back the word "ERROR" an handle it in my 
response.error-function ? Is this a JSON-encoding/decoding problem ?
Tried all to solve this issue but without success.
THX.</p>