AngularJS - Function Not Defined

With the below code, I'm trying to show a toast with AngularJS inside a Firebase function. The function is showToast() but I'm getting a function not defined error. Any help would be appreciated, thanks!

Function:

app.controller('PageCtrl', function($scope, $mdToast, $document) {
  function showToast() {
    $mdToast.show(
      $mdToast.simple()
      .textContent('Simple lala Toast!')
      .hideDelay(3000)
    );
  };
});

Attempt to call function:

function signInUser(email, password) {
  var email = document.getElementById('email-input').value;
  var password = document.getElementById('password-input').value;

  auth.signInWithEmailAndPassword(email, password).then(function(value) {
    // REDIRECT TO THE HOME PAGE AFTER LOGIN
    //window.location = "#/home";
    //location.reload();

    showToast();

  }).catch(function(error) {
    var errorCode = error.code;
    var errorMessage = error.message;

    if (errorCode == 'auth/invalid-email') {
      alert('That user does not exist.');
    } else {
      alert(errorMessage);
    }
    console.log(error);
  });
}

Full Script:

/*

INITIALIZATION

*/

// FIREBASE CONFIGURATION
var config = {
  apiKey: "AIzaSyA2_fVDRCKhCJ5QueXY-Xb2CxFFuxY-rdU",
  authDomain: "user-database-d1a70.firebaseapp.com",
  databaseURL: "https://user-database-d1a70.firebaseio.com",
  storageBucket: "user-database-d1a70.appspot.com",
  messagingSenderId: "528331985076"
};

// INITIALIZE FIREBASE
firebase.initializeApp(config);
var database = firebase.database();
var auth = firebase.auth();

// ANGULARJS APPLICATION
var app = angular.module('FirebaseTest', [
  'ngRoute', 'ngMaterial', 'ngMessages'
]);

/*

ROUTES

*/

app.config(['$routeProvider', function ($routeProvider) {
  $routeProvider
  .when("/home", {templateUrl: "partials/home.html", controller: "PageCtrl"})
  .when("/about", {templateUrl: "partials/about.html", controller: "PageCtrl"})
  .when("/faq", {templateUrl: "partials/faq.html", controller: "PageCtrl"})
  .when("/nutrition", {templateUrl: "partials/nutrition.html", controller: "PageCtrl"})
  .when("/login", {templateUrl: "partials/login.html", controller: "PageCtrl"})
  .when("/register", {templateUrl: "partials/register.html", controller: "PageCtrl"})
  .otherwise({redirectTo:"/home", template: "partials/home.html", controller: "PageCtrl"});
}]);

/*

CONTROLLERS

*/

app.controller('PageCtrl', function($scope) {

});

app.controller('NavCtrl', function($scope) {
  var url = document.URL;
  var array = url.split('/');
  var pathname = array[array.length-1];

  console.log("Pathname: "+pathname);
  $scope.currentNavItem = pathname;
});

app.controller('NutritionCtrl', function($scope) {
  $scope.user = {
    gender: 'Female',
    goal: 'Lose Weight'
  };

  $scope.genders = ('Male Female').split(' ').map(function(gender) {
    return {abbrev: gender};
  });
  $scope.goals = ('Lose Weight_Gain Weight').split('_').map(function(goal) {
    return {abbrev: goal};
  });
});

app.controller('PageCtrl', function($scope, $mdToast, $document) {
  function showToast() {
    $mdToast.show(
      $mdToast.simple()
        .textContent('Simple lala Toast!')
        .hideDelay(3000)
    );
  };
});

/*

METHODS

*/

// FIREBASE CREATE USER METHOD
function writeUserData(email, password) {
  auth.createUserWithEmailAndPassword(email, password)
  .then(function () {

  })
  .catch(function(error) {
    var errorCode = error.code;
    var errorMessage = error.message;

    if (errorCode == 'auth/weak-password') {
      alert('The password is too weak.');
    } else {
      alert(errorMessage);
    }
    console.log(error);
  });
}

// FIREBASE SIGN IN USER METHOD
function signInUser(email, password) {
  var email = document.getElementById('email-input').value;
  var password = document.getElementById('password-input').value;

  auth.signInWithEmailAndPassword(email, password).then(function(value) {
    // REDIRECT TO THE HOME PAGE AFTER LOGIN
    //window.location = "#/home";
    //location.reload();

    showToast();

  }).catch(function(error) {
    var errorCode = error.code;
    var errorMessage = error.message;

    if (errorCode == 'auth/invalid-email') {
      alert('That user does not exist.');
    } else {
      alert(errorMessage);
    }
    console.log(error);
  });
}

// FIREBASE SIGN OUT USER METHID
function signOutUser() {
  auth.signOut().then(function() {
    // REDIRECT TO THE HOME PAGE AFTER LOGOUT
    window.location = "#/home";
    location.reload();
  }, function(error) {
    // Errors go here.
  });
}

// FIREBASE AUTH STATE CHANGE METHOD
auth.onAuthStateChanged(function(user) {
  // NAVIGATION LINKS
  var nutritionLink = document.getElementById('nav-nutrition');

  // USER INFORMATION
  var user = firebase.auth().currentUser;

  if (user) {
    email = user.email;
    uid = user.uid;

    // HIDE/SHOW LINKS
    $(nutritionLink).show();

    // UPDATE HEADER TEXT WITH USER EMAIL
    document.getElementById('header-username').innerHTML="Logged in as " + email + " - <a href='#' onclick='return signOutUser(this);'>Sign Out</a>";

    console.log("Provider-specific UID: "+uid);
    console.log("Email: "+email);
  } else {

    // HIDE/SHOW LINKS
    $(nutritionLink).hide();

    // UPDATE HEADER TEXT WITH USER EMAIL
    document.getElementById('header-username').innerHTML="<a href='#/login'>Login/Register</a>";
  }
});

/*

FUNCTIONS

*/