Code must run error free and not rely on warnings and notices to be hidden to meet this requirement. For instance, never access a variable that you did not set yourself (such as $_POST array keys) without first checking to see that it isset() .
Make sure that your dev environment has error reporting enabled for ALL users, and that display_errors is enabled in the PHP environment. You can check this setting with:
On some servers where display_errors is disabled, and you do not have the ability to change this in the php.ini, you can often enable it with: