/usr/share/php/ is in php-symfony-yaml 2.3.21+dfsg-4+deb8u3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/php/Symfony/
/usr/share/php/Symfony/Component/
/usr/share/php/Symfony/Component/Yaml/
/usr/share/php/Symfony/Component/Yaml/Yaml.php
/usr/share/php/Symfony/Component/Yaml/Unescaper.php
/usr/share/php/Symfony/Component/Yaml/Parser.php
/usr/share/php/Symfony/Component/Yaml/Inline.php
/usr/share/php/Symfony/Component/Yaml/Exception/
/usr/share/php/Symfony/Component/Yaml/Exception/DumpException.php
/usr/share/php/Symfony/Component/Yaml/Exception/ExceptionInterface.php
/usr/share/php/Symfony/Component/Yaml/Exception/ParseException.php
/usr/share/php/Symfony/Component/Yaml/Exception/RuntimeException.php
/usr/share/php/Symfony/Component/Yaml/Escaper.php
/usr/share/php/Symfony/Component/Yaml/Dumper.php