Sample code for using the pmpro_after_all_membership_level_changes action.

my_pmpro_after_all_membership_level_changes_sample.php

<?php

/**
 * Sample code for using the pmpro_after_all_membership_level_changes action.
 *
 * @param array $old_user_levels $user_id => array $old_levels
 */
function my_pmpro_after_all_membership_level_changes_sample( $old_user_levels ) {
	// Step 1: Loop through $old_user_levels.
	foreach ( $old_user_levels as $user_id => $old_levels ) {
		// Step 2: Get the user's current membership levels.
		$new_levels = pmpro_getMembershipLevelsForUser( $user_id );

		// Step 3: Build arrays of "options" associated with old and new membership levels.
		$old_options = array();
		$new_options = array();
		// Populate $old_options.
		foreach ( $old_levels as $old_level ) {
			$old_level_options = array(); // TODO: Get array of options for $old_level.
			if ( ! empty( $old_level_options ) && is_array( $old_level_options ) ) {
				$old_options = array_merge( $old_options, $old_level_options );
			}
		}
		// Populate new_options.
		foreach ( $new_levels as $new_level ) {
			$new_level_options = array(); // TODO: Get array of options for $new_level.
			if ( ! empty( $new_level_options ) && is_array( $new_level_options ) ) {
				$new_options = array_merge( $new_options, $new_level_options );
			}
		}

		// Step 4: Remove duplicates in the array of old and new options.
		$new_options = array_unique( $old_options );		
		$old_options = array_unique( $new_options );

		// Step 5: Build the final array of options that needs to be added/removed for the current user.
		$add_options = array_values( array_diff( $new_options, $old_options ) );
		$remove_options = array_values( array_diff( $old_options, $new_options ) );

		// Step 6: Execute changes.
		foreach ( $add_options as $add_option ) {
			// TODO: Add the option for the user.
		}
		foreach ( $remove_options as $remove_option ) {
			// TODO: Remove the option from the user.
		}
	}
}
add_action( 'pmpro_after_all_membership_level_changes', 'my_pmpro_after_all_membership_level_changes_sample', 10, 1 );