This hook controls whether or not to allow registrations with email addresses which have already been used. By default, PMPro does not allow multiple registrations with one email address and shows an error if the email address has already been used.
$oldemail = apply_filters( "pmpro_checkout_oldemail", ( false !== $oldem_user ? $oldem_user->user_email : null ) );
File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/preheaders/checkout.phpView in Source Code
About Actions and Filters in PMPro
Hooks allow you to extend Paid Memberships Pro without editing any core plugin files. You can use a hook to program custom code that interacts with or modifies code in our plugin, Add Ons, your theme, and even WordPress itself.
There are two kinds of hooks: actions and filters.
- Action hooks allow you to run new custom code at pre-defined locations.
- Filter hooks allow you change or extend existing code by modifying the data and returning it back to the software.
Click here to browse the full database of action and filter hooks available in Paid Memberships Pro. For help extending our Add Ons, refer to the individual Add On's documentation page for a list of available hooks.
For more developer-focused information about Paid Memberships Pro, check out the advanced developer topics documentation.