my controller fails to find helper function

Your  helper is called myvalidate_helper, but the function you define inside it (I'm assuming) is named is_valid_level. There is no myvalidate function. There was no need to change your ci3 code. If you want to be sure the helper is being loaded do the following:

PHP Code:

helper('myvalidate');
if (!is_valid_level($level3)) { ... 


However, as you stated if you did this then you don't need to use the helper function to load the helper as the Controller will auto load it for you.

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