$r for eval

see line :341

eval($var.'="'.\str_replace('"', '\"', $itm).'";');

eval function parameter example：

$r["domain"]["name"]="aaa.com";

But $r is string

you see : https://www.php.net/manual/en/language.types.string.php

Warning:
Writing to an out of range offset pads the string with spaces. Non-integer types are converted to integer. Illegal offset type emits E_WARNING. Only the first character of an assigned string is used. As of PHP 7.1.0, assigning an empty string throws a fatal error. Formerly, it assigned a NULL byte.

sorry ,my English is poor...