Add a two character prefix to each log line, that remains the same over the...

Add a two character prefix to each log line, that remains the same over the lifetime of the request. This makes it easy to distinguish lines between requests that happen at the same time.

htdocs/lib/errors.php

@@ -122,6 +122,12 @@ function log_message ($message, $loglevel, $escape, $backtrace, $file=null, $lin
         require_once(get_config('docroot') . 'auth/lib.php');
         $SESSION = Session::singleton();
     }
+
+    static $requestprefix = '';
+    if (!$requestprefix) {
+        $requestprefix = substr(md5(microtime()), 0, 2) . ' ';
+    }
+
     static $loglevelnames = array(
         LOG_LEVEL_ENVIRON => 'environ',
         LOG_LEVEL_DBG     => 'dbg',
@@ -163,15 +169,13 @@ function log_message ($message, $loglevel, $escape, $backtrace, $file=null, $lin
     }
 
     // Make a prefix for each line, if we are logging a normal debug/info/warn message
+    $prefix = $requestprefix;
     if ($loglevel != LOG_LEVEL_ENVIRON && function_exists('get_config')) {
         $docroot = get_config('docroot');
         $prefixfilename = (substr($filename, 0, strlen($docroot)) == $docroot)
             ? substr($filename, strlen($docroot))
             : $filename;
-        $prefix = '(' . $prefixfilename . ':' . $linenum . ') ';
-    }
-    else {
-        $prefix = '';
+        $prefix .= '(' . $prefixfilename . ':' . $linenum . ') ';
     }
     $prefix = '[' . str_pad(substr(strtoupper($loglevelnames[$loglevel]), 0, 3), 3) . '] ' . $prefix;