force_https_set_url_scheme.php

<?php
add_filter( 'set_url_scheme', 'lc_force_secure_scheme', 10, 3 );
/**
 * Force all URLs run through the set_url_scheme to always be https if they're
 * being accessed through our reverse proxy.
 *
 * @param string      $url         The complete URL including scheme and path.
 * @param string      $scheme      Scheme applied to the URL. One of 'http', 'https', or 'relative'.
 * @param string|null $orig_scheme Scheme requested for the URL. One of 'http', 'https', 'login',
 *                                 'login_post', 'admin', 'relative', 'rest', 'rpc', or null.
 */
function lc_force_secure_scheme( $url, $scheme, $orig_scheme ) {

	if ( ! lc_is_reverse_proxy() )
		return $url;

	$scheme = 'https';

	$url = trim( $url );
	if ( substr( $url, 0, 2 ) === '//' )
		$url = 'http:' . $url;

	$url = preg_replace( '#^\w+://#', $scheme . '://', $url );

	return $url;

}