I’m refining my WordPress patient-registration flow and need a solid, server-side CPF check built directly into KiviCare. The goal is to run the full mathematical validation in PHP, immediately block any invalid or repeated sequences such as 111.111.111-11, and return a clear, human-readable error through the existing AJAX call that KiviCare uses. The form will become a three-step wizard: • Step 1 – Personal information: Name, Email and Phone Number • Step 2 – CPF plus any other required data, validated in real time via AJAX to the backend routine you create • Step 3 – Final review and user creation Only a CPF that passes the algorithm may proceed to account creation; on success the CPF is saved as user meta so it remains available throughout the KiviCare workflow. Everything must stay lightweight, responsive and compatible with Fluent Forms as well, in case I switch later. Deliverables 1. Backend PHP class or plugin that performs CPF digit verification, rejects repeated sequences and exposes an endpoint consumable by AJAX. 2. Integration into the current KiviCare registration form, converting it into the outlined multi-step layout without breaking existing styles. 3. Friendly error handling returned to the front end (inline or toast is fine as long as it’s clear and non-intrusive). 4. Documentation outlining function names, hooks used and where the CPF is stored so future updates remain painless. Once delivered I’ll test by submitting a range of valid and invalid CPFs; success means invalid entries are blocked, valid ones complete registration and the CPF appears correctly in user meta.