<?php

$status = get_user_meta( $id , 'wpcf-status' , true );

if( $status !== 'active' ) {
return;
}

$membership = get_user_meta( $id , 'wpcf-membership-id' , true ); //returns the ID for the membership to assign
$start_date = get_user_meta( $id , 'wpcf-start-date' , true ); //returns the start date for the membership in format 'Ymd'
$end_date = get_user_meta( $id , 'wpcf-expire-date' , true ); //returns the expire date to apply in format 'Ymd'

$api = ms_api();

$member = $api->get_member( $id );

$subscription = $member->add_membership( $membership );

if( $start_date !== '' ) {
$subscription->set_start_date( $start_date );
}

if( $end_date !== '' ) {
$subscription->set_expire_date( $end_date );
}
$subscription->status = MS_Model_Relationship::STATUS_ACTIVE;
$subscription->save();