framework/helpers/BaseHtml.php
public static function textarea($name, $value = '', $options = [])
    {
        $options['name'] = $name;
        $doubleEncode = ArrayHelper::remove($options, 'doubleEncode', true);
        return static::tag('textarea', static::encode($value, $doubleEncode), $options);
    }
public static function textarea($name, $value = '', $options = [])
    {
        $options['name'] = $name;
        $doubleEncode = ArrayHelper::remove($options, 'doubleEncode', true);
        return static::tag('textarea', static::encode($value, $doubleEncode), $options);
    }
Generates a text area input.
@param string $name the input name
@param string $value the input value. Note that it will be encoded using [[encode()]].
@param array $options the tag options in terms of name-value pairs. These will be rendered as
the attributes of the resulting tag. The values will be HTML-encoded using [[encode()]].
If a value is null, the corresponding attribute will not be rendered.
See [[renderTagAttributes()]] for details on how attributes are being rendered.
The following special options are recognized:

- `doubleEncode`: whether to double encode HTML entities in `$value`. If `false`, HTML entities in `$value` will not
be further encoded. This option is available since version 2.0.11.

@return string the generated text area tag