How to subtract two fields and show result in email

Hi, I have two fields {price} and {deposit}. I would like to subtract deposit from price and show the value in an email. I assume I need to add some PHP code within the 'SETUP' section that does the calculation and outputs the answer to a field, I can then add the Var to the email.
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I have searched the forums and can not find and example of how to write the PHP code.
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Any help would be really appreciated.
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Thanks. 🙂

$this->get("varname", "default value if not found"); for things you would get with {var}
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$this->data("field", "default"); for {data}

Hi, I am looking to subtract the {deposit} field from the {price} field and show the result as a VAR. I am not sure if the code you have provided would do that? Am I missing something?
Thanks

The code I gave you shows how to get a {var:} or {data:} value, since you can't use shortcode in PHP. Return the value you want, then display it elsewhere using {var:php_action_name}