update login function

app/Http/Controllers/UserController.php

@@ -26,11 +26,13 @@ public function register(RegisterRequest $request){
 
     public function login(LoginRequest $request){
         $user = User::where('phone', $request->phone)->get();
-        for ($i = 0; $i < count($user); $i++){
-            if ($user[$i]->password == md5($request->password))
-                return 'Login success';
-            else return 'Login fail';
-        } 
+        if ($user->count()){
+            for ($i = 0; $i < count($user); $i++){
+                if ($user[$i]->password == md5($request->password))
+                    return 'Login success';
+                else return 'Login fail';
+            } 
+        } else return 'Tai khoan khong ton tai';
     }
 
 }