I came to problem with this Can't open file in php if one of directories is a symlink
suhosin ducumentation said that suhosin.executor.allow_symlink
This flag reactivates symlink() when open_basedir is used, which is disabled by default in Suhosin >= 0.9.6. Allowing symlink() while open_basedir is used is actually a security risk.
Why it's security problem, what can happen if it's set to Off or when I use root directory in open_basedir?
symlinks make it trivial to 'break out' of the pseudo-chroot jail that a webserver's DocumentRoot imposes. With symlinks on, you can point at ANY file/directory on the server, and the webserver will happily follow the symlink, never knowing it's left the confines of the DocumentRoot. Consider what could happen if you had:
ln -s /etc/shadow /www/docroot/index.html
ln -s /etc/passwd /www/docroot/index2.html