/usr/share/php/data/ApiGen/theme-bootstrap/resources/bootstrap.min.css is in php-apigen-theme-bootstrap 1.1.3+dfsg-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/php/data/ApiGen/theme-bootstrap/resources/../../../../../javascript/bootstrap/css/bootstrap.min.css