Adding telephone field using Register Helper

rh-telephone.php

<?php

//copy from line 5 downwards into your customization plugin

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();
    $fields[] = new PMProRH_Field(
        "Telephone",              // input name, will also be used as meta key
        "text",                 // type of field
        array(
            "label" => "Telephone Number",
            "size"=>30,         // input size
            "profile"=>true,    // show in user profile
            "required"=>true    // make this field required
        ));
    //add the fields into a new checkout_boxes are of the checkout page
    foreach($fields as $field)
        pmprorh_add_registration_field(
            "after_billing_fields", // 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");