framework/helpers/BaseVarDumper.php
public static function dumpAsString($var, $depth = 10, $highlight = false)
    {
        self::$_output = '';
        self::$_objects = [];
        self::$_depth = $depth;
        self::dumpInternal($var, 0);
        if ($highlight) {
            $result = highlight_string("<?php\n" . self::$_output, true);
            self::$_output = preg_replace('/&lt;\\?php<br \\/>/', '', $result, 1);
        }

        return self::$_output;
    }
public static function dumpAsString($var, $depth = 10, $highlight = false)
    {
        self::$_output = '';
        self::$_objects = [];
        self::$_depth = $depth;
        self::dumpInternal($var, 0);
        if ($highlight) {
            $result = highlight_string("<?php\n" . self::$_output, true);
            self::$_output = preg_replace('/&lt;\\?php<br \\/>/', '', $result, 1);
        }

        return self::$_output;
    }
Dumps a variable in terms of a string.
This method achieves the similar functionality as var_dump and print_r
but is more robust when handling complex objects such as Yii controllers.
@param mixed $var variable to be dumped
@param int $depth maximum depth that the dumper should go into the variable. Defaults to 10.
@param bool $highlight whether the result should be syntax-highlighted
@return string the string representation of the variable