Dynamically display certain levels on the Membership Levels page based on the current user's active level

dynamic_pmpro_levels_array.php

<?php
/**
 * Dynamically display certain levels on the Membership Levels page based on the current user's active level
 * This example allows you to show/hide specific levels on the Membership Levels page.
 */
function dynamic_pmpro_levels_array( $levels ) {	
	// Get all the levels
	$levels = pmpro_getAllLevels( false, true );
	
	// remove levels 1, 5, 6, and 7 user has level 1.
	if ( pmpro_hasMembershipLevel( '1' ) ) {
		unset( $levels['1'] );
		unset( $levels['5'] );
		unset( $levels['6'] );
		unset( $levels['7'] );
	}
	// remove levels 1, 2, 3, and 4 if user has level 2.
	if ( pmpro_hasMembershipLevel( '2' ) ) {
		unset( $levels['1'] );
		unset( $levels['2'] );
		unset( $levels['3'] );
		unset( $levels['4'] );
	}
	// only show levels 1 and 2 if user has no level.
	if ( ! pmpro_hasMembershipLevel( ) ) {
		unset( $levels['3'] );
		unset( $levels['4'] );
		unset( $levels['5'] );
		unset( $levels['6'] );
		unset( $levels['7'] );
	}	
	return $levels;
}
add_filter( 'pmpro_levels_array', 'dynamic_pmpro_levels_array', 10, 2 );