Example Register Helper field that displays as read only to the user on the WordPress profile page.

readonly-on-profile-example.php

<?php

/**
 * PMPro Customization: Register Helper - Add date of birth date picker to checkout
 * Display field as read-only for user but as editable field for administrators
 */

//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;
	}

	$fields   = array();

	$fields[] = new PMProRH_Field(
		'date_of_birth', // input name, will also be used as meta key
		'date', // type of field
		array(
			'label'          => 'Date Of Birth', // custom field label
			'class'          => 'date', // date class
			'profile'        => 'admin', // show in registration form but only show to administrators in user profile,
			'required'       => true, // make this field required
			'addmember'      => true, // show in Add Member
			'memberslistcsv' => true, // Include in Member List CSV Export
		)
	);
  // display as readonly in the backend if user not an administrator
	if ( is_admin() && ! current_user_can( 'manage_options' ) ) {
		$fields[] = new PMProRH_Field(
			'date_of_birth', // input name, will also be used as meta key
			'readonly', // type of field
			array(
				'label'   => 'Date Of Birth', // custom field label
				'class'   => 'date', // date class
				'profile' => 'only', // show in user profile only
			)
		);
	}
	//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' );