chickadee/site_actions.php

<?php
  include_once "logcheck.php";

  $simplecss = $_POST["simplecss"] ?? null;
  if ( !is_null( $simplecss ) ) {
    $file_data = file_get_contents( "config.php" );
		if ( !$file_data ) {
			header("Location: admin.php?success=0");
			die();
		}
		$re = '/(const\s+SIMPLE_CSS\s+=\s+)(true|false)(\s*;)/m';
    $subst = $simplecss == "1" ? "$1true$3" : "$1false$3";
		$result = preg_replace($re, $subst, $file_data);
		$success = file_put_contents( "config.php", $result );
		if ( $success ) {
			header("Location: admin.php?success=2");
			die();
		} else {
			header("Location: admin.php?success=0");
			die();
		}
  }

	header("Location: admin.php");
  die();