extension.driver.php

<?php
	
	class extension_page_headers extends Extension {
		
		private $headersTrigger;
		
		public function about() {
			return array(
				'name'			=> 'Page Headers',
				'version'		=> '1.2',
				'release-date'	=> '2012-06-06',
				'author'		=> array(
					'name'			=> 'Henry Singleton',
					'website'		=> 'http://henrysingleton.com'
				),
				'description' => 'Allows headers to be output as part of page content, overwriting existing headers.'
			);
		}
		
		public function uninstall() {
			return true;
		}
		
		public function install() {
			return true;
		}
		
		public function getSubscribedDelegates() {
			return array(
				array(
					'page'		=> '/frontend/',
					'delegate'	=> 'FrontendPageResolved',
					'callback'	=> 'checkHeadersPageType'
				),
				array(
					'page'		=> '/frontend/',
					'delegate'	=> 'FrontendOutputPostGenerate',
					'callback'	=> 'processPageContent'
				)
			);
		}
		
		public function checkheadersPageType($page) {
			//Check that the page type has been sent to 'headers' so we only process a page when we need to. 
			if (is_array($page) &&
				is_array($page['page_data']) &&
				array_key_exists('type', $page['page_data']) &&
				array_search('headers',$page['page_data']['type']) !== false
			) {
					$this->headersTrigger = true;
			}
		}
		
		public function processPageContent($page) {
			//If this page has 'headers' set as a page type, process the content.
			if ($this->headersTrigger === true) {
				$content = $page['output'];
						
				if (
					
					//If the content is false that means there is likely a symphony error being shown. If so, don't do anything. 
					$content !== false &&
					
					//Just check that the page content doesn't start with an angle bracket, as that would mean XML/HTML was probably being output and not the sweet juicy headers we crave.
					strpos($content, '<') !== 0 && 
					
					//Check we haven't already sent the headers, to avoid nasty PHP error.
					!headers_sent()
					
				) {	
					//split response by two consecutive newlines (as per http sepc)
					$parts = explode("\n\n", $content);
					
					//grab the block before the first two newlines, and then split by newlines for each header
					$headers = explode("\n",array_shift($parts));
					
					if (is_array($headers)) {
						
						//Send each found header
						foreach ($headers as $header) {
							header(trim($header));
						}
						
						//Turn parts back into string, with headers absent due to array_unshift above
						$page['output'] = trim(implode("\n", $parts));
						
						//If only headers were used in the page output, kill the script now, as we have nothing else to send, and a Symphony error will be generated if the output is empty.
						if (strlen($page['output']) === 0) die();
					}
				}
			}
		}		
	}