my_pmpro_default_registration_level

my_pmpro_default_registration_level.php

<?php
/**
	* When registering, add the member to a specific membership level 
	* @param integer $user_id
**/

//Disables the pmpro redirect to levels page when user tries to register
add_filter("pmpro_login_redirect", "__return_false");

function my_pmpro_default_registration_level($user_id) {
	//Give all members who register membership level 1
	pmpro_changeMembershipLevel(1, $user_id);
}
add_action('user_register', 'my_pmpro_default_registration_level');
?>

To inherit level & expiration settings, please see: https://gist.github.com/andrewlimaza/563be9bf3a0b369fa3747ec78cad1513