Make any post older than 18 months available for free with Paid Memberships Pro.

make_old_posts_free.php

<?php
/**
 * Allow non-members to view restricted posts if they are less than 30 days old. 
 * Change the '-30 Days' below if you'd like to allow access for longer or shorter.
 * Adjust $categories array for the categories this should apply to.
 * Add this code to your Customizations Plugin by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function open_new_posts_to_non_members($hasaccess, $thepost, $theuser, $post_membership_levels) {
	global $wpdb;

	//if PMPro says true already, return true
	if ( $hasaccess ) {
		return $hasaccess;	
    }

    // Categories that this code should apply to. Categories not here will assume default functionality.
    $categories = array( 'category-1', 'category-2' );

    if ( ! in_category( $categories, $thepost ) ) {
        return $hasaccess;
    }

	//figure out dates to check
	$cutoff = strtotime( '-30 Days', current_time( 'timestamp' ) );
	$published = strtotime( $thepost->post_date, current_time('timestamp') );
	
	//if published after the cuttoff, then allow access for now
	if ( $published > $cutoff ) {
        $hasaccess = true;
    }
	
	return $hasaccess;
}
add_filter("pmpro_has_membership_access_filter", "open_new_posts_to_non_members", 20, 4);

I am looking to leave patreon and this is a HUGE step in making PMP acting like the early access feature in patreon. Thank you!