pmpro-one-time-signup-fee.php

<?php

/**
 * This will allow you to charge additional extras on the user's fee.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

 
 //we have to put everything in a function called on init, so we are sure Register Helper is loaded
function my_pmprorh_init()
{
    //don't break if Register Helper is not loaded
    if(!function_exists( 'pmprorh_add_registration_field' )) {
        return false;
    }
    
    //define the fields
    $fields = array();
    $fields[] = new PMProRH_Field(
        'signupfee',                       // input name, will also be used as meta key
        'checkbox',                         // type of field
        array(
            'label'     => 'Signup Fee $30',       // custom field label
            'hint'       => 'I understand there is a new members fee',
            'levels'    => 1,
            'required'  => true,
        )
    );

    
    //add the fields into a new checkout_boxes are of the checkout page
    foreach($fields as $field)
        pmprorh_add_registration_field(
            'checkout_boxes',               // location on checkout page
            $field                      // PMProRH_Field object
        );
    //that's it. see the PMPro Register Helper readme for more information and examples.
}
add_action( 'init', 'my_pmprorh_init' );


function my_pmpro_checkout_level($level)
{
  if ( ! empty( $_REQUEST['signupfee'] ) ) {
     $level->initial_payment = $level->initial_payment + 30; //to update the initial payment.
   // $level->billing_amount = $level->billing_amount + 175;  //to update recurring payments too
  }
 
  return $level;
}
add_filter( 'pmpro_checkout_level', 'my_pmpro_checkout_level' );