Add output buffering to AJAX requests

Fixes #443.
Extract output buffering to function.
Use regular buffering if gzip option not set.
Use buffering in AJAX requests, to avoid “headers already sent” warning
in some situations.

qa-include/qa-ajax.php

@@ -80,6 +80,7 @@
 	if (isset($routing[$operation])) {
 		qa_db_connect('qa_ajax_db_fail_handler');
 
+		qa_initialize_buffering();
 		require QA_INCLUDE_DIR.'ajax/'.$routing[$operation];
 
 		qa_db_disconnect();

qa-include/qa-base.php

@@ -319,6 +319,23 @@
 	}
 
 
+	/**
+	 * Set up output buffering. Use gzip compression if option set and it's not an admin page (since some of these contain lengthy processes).
+	 * @param $request
+	 * @return bool whether buffering was used
+	 */
+	function qa_initialize_buffering($request='')
+	{
+		if (headers_sent()) {
+			return false;
+		}
+
+		$useGzip = QA_HTML_COMPRESSION && substr($request, 0, 6) !== 'admin/' && extension_loaded('zlib');
+		ob_start($useGzip ? 'ob_gzhandler' : null);
+		return true;
+	}
+
+
 	function qa_register_core_modules()
 /*
 	Register all modules that come as part of the Q2A core (as opposed to plugins)

qa-include/qa-index.php

@@ -182,11 +182,7 @@
 			require QA_INCLUDE_DIR.'qa-url-test.php';
 		else {
 			// enable gzip compression for output (needs to come early)
-			// skip admin pages since some of these contain lengthy processes
-			if (QA_HTML_COMPRESSION && substr($requestlower, 0, 6) != 'admin/') {
-				if (extension_loaded('zlib') && !headers_sent())
-					ob_start('ob_gzhandler');
-			}
+			qa_initialize_buffering($requestlower);
 
 			if (substr($requestlower, 0, 5) == 'feed/')
 				require QA_INCLUDE_DIR.'qa-feed.php';