Issue #3: check headers already sent (#13)

Author: herbdool

httpbl.module

@@ -147,7 +147,10 @@ function httpbl_boot() {
 
     $message = strtr($message, array('%ip' => ip_address(), '%ipurl' => _httpbl_ipdata(ip_address(), FALSE), '%honeypot' => $link, '%whitelisturl' => _httpbl_url('/httpbl/whitelist')));
 
-    header('HTTP/1.1 403 Forbidden');
+    if (!headers_sent()) {
+      header('HTTP/1.1 403 Forbidden');
+    }
+
     echo $message;
     exit();
   }