Add Log to STDOUT Feature (#5721)

Primarily useful for PHP applications running under PHP-FPM which in
turn is running within a Docker container. But also it is generally
useful in any situation where you want to be able to send the logs
directly to your terminal when debugging &etc.

config/defaults.inc.php

@@ -66,7 +66,7 @@
 // system error reporting, sum of: 1 = log; 4 = show
 $config['debug_level'] = 1;
 
-// log driver:  'syslog' or 'file'.
+// log driver:  'syslog', 'stdout' or 'file'.
 $config['log_driver'] = 'file';
 
 // date format for log entries

installer/config.php

@@ -216,11 +216,11 @@
 <?php
 
 $select_log_driver = new html_select(array('name' => '_log_driver', 'id' => "cfglogdriver"));
-$select_log_driver->add(array('file', 'syslog'), array('file', 'syslog'));
+$select_log_driver->add(array('file', 'syslog', 'stdout'), array('file', 'syslog', 'stdout'));
 echo $select_log_driver->show($RCI->getprop('log_driver', 'file'));
 
 ?>
-<div>How to do logging? 'file' - write to files in the log directory, 'syslog' - use the syslog facility.</div>
+<div>How to do logging? 'file' - write to files in the log directory, 'syslog' - use the syslog facility, 'stdout' writes to the process' STDOUT file descriptor.</div>
 </dd>
 
 <dt class="propname">log_dir</dt>

program/lib/Roundcube/rcube.php

@@ -1221,6 +1221,13 @@ public static function write_log($name, $line)
             return syslog($prio, $line);
         }
 
+        // write message with file name when configured to log to STDOUT
+        if ($log_driver == 'stdout') {
+            $stdout = "php://stdout";
+            $line = "$name: $line";
+            return file_put_contents($stdout, $line, FILE_APPEND) !== false;
+        }
+
         // log_driver == 'file' is assumed here
 
         $line = sprintf("[%s]: %s\n", $date, $line);