Writers | Zend_Log Programmer's Reference Guide | Filters

# Formatters

A Formatter is an object that is responsible for taking an `event` array describing a log event and outputting a string with a formatted log line.

Some Writers are not line-oriented and cannot use a Formatter. An example is the Database Writer, which inserts the event items directly into database columns. For Writers that cannot support a Formatter, an exception is thrown if you attempt to set a Formatter.

# Simple Formatting

Zend_Log_Formatter_Simple is the default formatter. It is configured automatically when you specify no formatter. The default configuration is equivalent to the following:

1. $format = '%timestamp% %priorityName% (%priority%): %message%' . PHP_EOL;
2. $formatter = new Zend_Log_Formatter_Simple($format);

A formatter is set on an individual Writer object using the Writer's setFormatter() method:

1. $writer = new Zend_Log_Writer_Stream('php://output');
2. $formatter = new Zend_Log_Formatter_Simple('hello %message%' . PHP_EOL);
3. $writer->setFormatter($formatter);
5. $logger = new Zend_Log();
6. $logger->addWriter($writer);
8. $logger->info('there');
10. // outputs "hello there"

The constructor of Zend_Log_Formatter_Simple accepts a single parameter: the format string. This string contains keys surrounded by percent signs (e.g. `%message%`). The format string may contain any key from the event data array. You can retrieve the default keys by using the DEFAULT_FORMAT constant from Zend_Log_Formatter_Simple.

# Formatting to XML

Zend_Log_Formatter_Xml formats log data into XML strings. By default, it automatically logs all items in the event data array:

1. $writer = new Zend_Log_Writer_Stream('php://output');
2. $formatter = new Zend_Log_Formatter_Xml();
3. $writer->setFormatter($formatter);
5. $logger = new Zend_Log();
6. $logger->addWriter($writer);
8. $logger->info('informational message');

The code above outputs the following XML (space added for clarity):

1. <logEntry>
2. <timestamp>2007-04-06T07:24:37-07:00</timestamp>
3. <message>informational message</message>
4. <priority>6</priority>
5. <priorityName>INFO</priorityName>
6. </logEntry>

It's possible to customize the root element as well as specify a mapping of XML elements to the items in the event data array. The constructor of Zend_Log_Formatter_Xml accepts a string with the name of the root element as the first parameter and an associative array with the element mapping as the second parameter:

1. $writer = new Zend_Log_Writer_Stream('php://output');
2. $formatter = new Zend_Log_Formatter_Xml('log',
3. array('msg' => 'message',
4. 'level' => 'priorityName')
5. );
6. $writer->setFormatter($formatter);
8. $logger = new Zend_Log();
9. $logger->addWriter($writer);
11. $logger->info('informational message');

The code above changes the root element from its default of `logEntry` to `log`. It also maps the element `msg` to the event data item `message`. This results in the following output:

1. <log>
2. <msg>informational message</msg>
3. <level>INFO</level>
4. </log>

Writers | Zend_Log Programmer's Reference Guide | Filters