Changing a php var form payment handling - php

Question

Context: I'm creating a WordPress website where users can upload their own posts via frontend by paying a posting fee.
Here is how it works: the user uploads their post data inside a form created with the plugin WP User Frontend Pro; once they click on the "submit" button, they are redirected to the payment page and, once the payment is complete, the system handles the PayPal IPN confirmation and publishes the post.
I have this code snippet created by WP User Frontend Pro that handles the PayPal gateway:
<?php
public function prepare_to_send( $data ) {
$user_id = $data['user_info']['id'];
$listener_url = add_query_arg( 'action', 'wpuf_paypal_success', home_url( '' ) );
//$listener_url = 'http://a53d2f68b609.ngrok.io/?action=wpuf_paypal_success';
//$listener_url = 'https://wpuf.sharedwithexpose.com/?action=wpuf_paypal_success';
$redirect_page_id = wpuf_get_option( 'payment_success', 'wpuf_payment' );
if ( $redirect_page_id ) {
$return_url = add_query_arg( 'action', 'wpuf_paypal_success', untrailingslashit( get_permalink( $redirect_page_id ) ) );
} else {
$return_url = add_query_arg( 'action', 'wpuf_paypal_success', untrailingslashit( get_permalink( wpuf_get_option( 'subscription_page', 'wpuf_payment' ) ) ) );
}
$billing_amount = empty( $data['price'] ) ? 0 : $data['price'];
if ( isset( $_POST['coupon_id'] ) && ! empty( $_POST['coupon_id'] ) ) {
$billing_amount = WPUF_Coupons::init()->discount( $billing_amount, $_POST['coupon_id'], $data['item_number'] );
$coupon_id = $_POST['coupon_id'];
} else {
$coupon_id = '';
}
$data['subtotal'] = $billing_amount;
$billing_amount = apply_filters( 'wpuf_payment_amount', $data['subtotal'] );
$data['tax'] = $billing_amount - $data['subtotal'];
if ( $billing_amount == 0 ) {
wpuf_get_user( $user_id )->subscription()->add_pack( $data['item_number'], $profile_id = null, false, 'free' );
wp_redirect( $return_url );
exit();
}
if ( $data['type'] == 'pack' && $data['custom']['recurring_pay'] == 'yes' ) {
if ( $data['custom']['cycle_period'] == 'day' ) {
$period = 'D';
} elseif ( $data['custom']['cycle_period'] == 'week' ) {
$period = 'W';
} elseif ( $data['custom']['cycle_period'] == 'month' ) {
$period = 'M';
} elseif ( $data['custom']['cycle_period'] == 'year' ) {
$period = 'Y';
}
if ( $data['custom']['trial_duration_type'] == 'day' ) {
$trial_period = 'D';
} elseif ( $data['custom']['trial_duration_type'] == 'week' ) {
$trial_period = 'W';
} elseif ( $data['custom']['trial_duration_type'] == 'month' ) {
$trial_period = 'M';
} elseif ( $data['custom']['trial_duration_type'] == 'year' ) {
$trial_period = 'Y';
}
$paypal_args = [
'cmd' => '_xclick-subscriptions',
'business' => wpuf_get_option( 'paypal_email', 'wpuf_payment' ),
'a3' => $billing_amount,
'mc_amount3' => $billing_amount,
'p3' => ! empty( $data['custom']['billing_cycle_number'] ) ? $data['custom']['billing_cycle_number'] : '0',
't3' => $period,
'item_name' => $data['custom']['post_title'],
'custom' => json_encode(
[
'billing_amount' => $billing_amount,
'type' => $data['type'],
'user_id' => $user_id,
'coupon_id' => $coupon_id,
'subtotal' => $data['subtotal'],
'tax' => $data['tax'],
]
),
'shipping' => 0,
'no_note' => 1,
'currency_code' => $data['currency'],
'item_number' => $data['item_number'],
'rm' => 2,
'return' => $return_url,
'cancel_return' => $return_url,
'notify_url' => $listener_url,
'src' => 1,
'sra' => 1,
'srt' => intval( $data['custom']['billing_limit'] ),
'recurring' => 1,
];
if ( $data['custom']['trial_status'] == 'yes' ) {
$paypal_args['p1'] = $data['custom']['trial_duration'];
$paypal_args['t1'] = $trial_period;
$paypal_args['a1'] = 0;
}
} else {
$paypal_args = [
'cmd' => '_xclick',
'business' => wpuf_get_option( 'paypal_email', 'wpuf_payment' ),
'amount' => $billing_amount,
'item_name' => isset( $data['custom']['post_title'] ) ? $data['custom']['post_title'] : $data['item_name'],
'no_shipping' => '1',
'shipping' => '0',
'no_note' => '1',
'currency_code' => $data['currency'],
'item_number' => $data['item_number'],
'charset' => 'UTF-8',
'rm' => '2',
'custom' => json_encode(
[
'type' => $data['type'],
'user_id' => $user_id,
'coupon_id' => $coupon_id,
'subtotal' => $data['subtotal'],
'tax' => $data['tax'],
]
),
'return' => $return_url,
'notify_url' => $listener_url,
];
}
$this->set_mode();
?>
What I'm focusing on here is the $billing_amount var.
At the moment, this var value is declared via a setting inside the plugin and it is a fixed number value: what I can do is simply change the "posting fee" by changing the value inside the plugin's form settings.
I would like, if possible, to change the value based on some radio/checkbox input fields that the user selects inside the posting form that comes before the payment page (as described before). I already know how to change an input value via JS, but I have no idea on how I could pass this JS value to the $billing_amount var.