/usr/share/php/ is in php-symfony-class-loader 3.4.6+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/php/Symfony/
/usr/share/php/Symfony/Component/
/usr/share/php/Symfony/Component/ClassLoader/
/usr/share/php/Symfony/Component/ClassLoader/ApcClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/ClassCollectionLoader.php
/usr/share/php/Symfony/Component/ClassLoader/ClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/ClassMapGenerator.php
/usr/share/php/Symfony/Component/ClassLoader/MapClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/Psr4ClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/WinCacheClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/XcacheClassLoader.php
/usr/share/php/Symfony/Component/ClassLoader/autoload.php