wkw/README.md

## README.md

      
    Raw
  

              README.md
            
          
    Controlled WPEngine Cache Busting

This technique was used to control WPEngine's caching by making WPE think there was a WordPress CMS user logged in by setting a fake cookie.
This code was developed to display site-wide dynamic content when a user authenticated against an external (non-WordPress) service.
N.B.: this worked as of 10/2015, but WPE may make infratructure changes which break the technique.
Usage

When you need to disable caching, call maybe_set_user_cookie(). This function must be called on every page load until you no longer need to disable caching. To stop the caching and remove the fake cookie, call remove_user_cookie().
Typical usage would be to set the cookie just before you need it and continue to set it until caching can be enabled again for the current user.

  
## bust-wpengine-cache.php
<?php
  /**
   * set a fake logged-in user cookie to break out of
   * wpe's caching as needed. Is only set if no other
   * CMS logged-in-user cookie has been set already.
   *
   * @return boolean true if new cookie set. false otherwise
   */
  function maybe_set_user_cookie() {

    $cookie_was_set = false;

    if ( false === ($cook = has_logged_in_user_cookie()) ) {
      $expire = time()+3600;  # modify expiration time to suit your needs
      set_fake_user_logged_in_cookie($expire);
      $cookie_was_set = true;
    }

    return $cookie_was_set;

  }

  # unset fake CMS user cookie
  function remove_user_cookie() {
    $expired = time()-3600;
    set_fake_user_logged_in_cookie($expired);
  }

  function set_fake_user_logged_in_cookie($expire=0) {
    $fake_user = '_fake_user_';
    $cookie = 'wordpress_logged_in_' . md5($fake_user);
    $value = md5($fake_user);
    setcookie($cookie, $value, $expire, '/');
  }

  # determine if logged-in cookie is already set
  function has_logged_in_user_cookie() {
    $patt = 'wordpress_logged_in_';
    foreach($_COOKIE as $cook => $val) {
      if( 0 === strpos($cook, $patt) ) {
        return $cook;
      }
    }
    return FALSE;
  }
	<?php
	/**
	* set a fake logged-in user cookie to break out of
	* wpe's caching as needed. Is only set if no other
	* CMS logged-in-user cookie has been set already.
	*
	* @return boolean true if new cookie set. false otherwise
	*/
	function maybe_set_user_cookie() {

	$cookie_was_set = false;

	if ( false === ($cook = has_logged_in_user_cookie()) ) {
	$expire = time()+3600; # modify expiration time to suit your needs
	set_fake_user_logged_in_cookie($expire);
	$cookie_was_set = true;
	}

	return $cookie_was_set;

	}

	# unset fake CMS user cookie
	function remove_user_cookie() {
	$expired = time()-3600;
	set_fake_user_logged_in_cookie($expired);
	}

	function set_fake_user_logged_in_cookie($expire=0) {
	$fake_user = '_fake_user_';
	$cookie = 'wordpress_logged_in_' . md5($fake_user);
	$value = md5($fake_user);
	setcookie($cookie, $value, $expire, '/');
	}

	# determine if logged-in cookie is already set
	function has_logged_in_user_cookie() {
	$patt = 'wordpress_logged_in_';
	foreach($_COOKIE as $cook => $val) {
	if( 0 === strpos($cook, $patt) ) {
	return $cook;
	}
	}
	return FALSE;
	}