What are formatter in Yii2 ?

Formatter is a Yii application component that is used to view data in readable format for users. By default, the formatter is implemented by yii\i18n\Formatter which provides a set of methods to format data as date/time, numbers, currencies, and other commonly used formats. You can use the format like the following,

$formatter = \Yii::$app->formatter;

// output: January 1, 2014
echo $formatter->asDate('2014-01-01', 'long');
 
// output: 12.50%
echo $formatter->asPercent(0.125, 2);
 
// output: cebe@example.com
echo $formatter->asEmail('cebe@example.com'); 

// output: Yes
echo $formatter->asBoolean(true); 
// it also handles display of null values:

// output: (not set)
echo $formatter->asDate(null);