[Firebase + Angular] AngularJS conversion to Firebase

I am trying to convert a simple little search app from a PHP endpoint to
Firebase.

I have converted the controller over and it is working to display the data
from firebase.

OLD PHP Endpoint

app.controller('InstantSearchController', ['$scope', '$http', function($scope, $http) {
     $http.get('inc/api.php').success(function(itemData) {
         $scope.items = itemData;
     });}]);

New Firebase Endpoint

app.controller('InstantSearchController', ['$scope', '$firebase', function($scope, $firebase) {
     var medRef = new Firebase("https://dazzling-fire-####.firebaseio.com/");
     $scope.items = $firebase(medRef);}]);

But I am not 100% sure how to swap the app.filter over to use the firebase
data.

Here is what it was with the PHP End Point

app.filter('searchFor', function(){

   return function(arr, searchString){
     if(!searchString){
       return arr;
     }
     var result = [];
     searchString = searchString.toLowerCase();
     angular.forEach(arr, function(item){
       if(item.english.toLowerCase().indexOf(searchString) !== -1){
         result.push(item);
       }
       if(item.spain.toLowerCase().indexOf(searchString) !== -1){
         result.push(item);
       }
       if(item.germany.toLowerCase().indexOf(searchString) !== -1){
         result.push(item);
       }
       if(item.france.toLowerCase().indexOf(searchString) !== -1){
         result.push(item);
       }
       if(item.philippines.toLowerCase().indexOf(searchString) !== -1){
         result.push(item);
       }
       });
     return result;
   };
});

And this is what I was thinking "should" work but it doesn't, from doing
some reading and watching of some tutorials i thought that i needed to
switch item with id

app.filter('searchFor', function(){

   return function(arr, searchString){
     if(!searchString){
       return arr;
     }
     var result = [];
     searchString = searchString.toLowerCase();
     return function(arr, searchString){
       if(!searchString){
         return arr;
       }
       var result = [];
       searchString = searchString.toLowerCase();
       angular.forEach(arr, function(id){
         if(id.english.toLowerCase().indexOf(searchString) !== -1){
           result.push(item);
         }
         if(id.spain.toLowerCase().indexOf(searchString) !== -1){
           result.push(item);
         }
         if(id.germany.toLowerCase().indexOf(searchString) !== -1){
           result.push(item);
         }
         if(id.france.toLowerCase().indexOf(searchString) !== -1){
           result.push(item);
         }
         if(id.philippines.toLowerCase().indexOf(searchString) !== -1){
           result.push(item);
         }
         });
       return result;
     };});

Any help pointing me in the right direction would be great i am really
trying to learn this AngularJS/Firebase stuff!