I think it's necessary to make that comparison because there are plugins like this 
http://www.eha.ee/labs/yiiplay/index.php/en/site/extension?view=dynamicrows

that deleting one row $ count does not change me explain better:
there are 4 rows and ids that are as follows (0,1,2,3), if I delete the 1 are so (0,2,3) without reorganize

```php
isset($_POST[get_class($model)][$count])
```
then that line would help you actually compare this index exists in the $ _POST