How to assign value to $_POST[ 'billing_phone' ] variable from another variable?

Question

WordPress

added a phone number to the WordPress registration form with this:

update_user_meta( $user_id, 'user_phone', sanitize_text_field( $_POST[ 'user_phone' ] ) );

how now to make this variable also assigned to the value $_POST['billing_phone']- the delivery phone in wokomers and displayed in the admin panel?

update_user_meta( $user_id, 'user_phone', sanitize_text_field( $_POST[ 'user_phone' ] ) );
update_user_meta( $user_id, 'user_phone', sanitize_text_field( $_POST[ 'billing_phone' ] ) );

and:

update_user_meta( $user_id, 'user_phone', sanitize_text_field( $_POST[ 'user_phone' ] ) );
$_POST[ 'billing_phone' ] = $_POST[ 'user_phone' ];

don't work... the first doesn't assign anything to anyone at all, the second doesn't assign anything $_POST[ 'billing_phone' ]...

Answer 1

$_POST[ 'billing_phone' ] = $_POST[ 'user_phone' ];