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12.4. File Permissions

If only you and people you trust can log into your web server, you don't need to worry about file permissions for files created by your PHP programs. However, most web sites are hosted on ISP's machines, and there's a risk that untrusted people will try to read files that your PHP program creates. There are a number of techniques that you can use to deal with file permissions issues.

12.4.4. Safe Mode

Many ISPs have scripts from several users running on one web server. Since all the users who share such a server run their PHP scripts as the same user, one script can read another's data files. Safe mode is an attempt to address this and other problems caused by shared servers. If you're not sharing your server with other users that you don't trust, you don't need to worry about safe mode at all.

When enabled through the safe_mode directive in your php.ini file, or on a per-directory or per-virtual host basis in your httpd.conf file, the following restrictions are applied to PHP scripts:

To configure safe_mode and the various related settings, you can set the serverwide default in your php.ini file like this:

safe_mode = On
safe_mode_include_dir = /usr/local/php/include
safe_mode_exec_dir = /usr/local/php/bin
safe_mode_gid = On
safe_mode_allowed_env_vars = PHP_
safe_mode_protected_env_vars = LD_LIBRARY_PATH

Alternately, you can set these from your httpd.conf file using the php_admin_value directive. Remember, these are system-level settings, and they cannot be set in your .htaccess file.

<VirtualHost 1.2.3.4>
  ServerName domainA.com
  DocumentRoot /web/sites/domainA
  php_admin_value safe_mode On
  php_admin_value safe_mode_include_dir /usr/local/php/include
  php_admin_value safe_mode_exec_dir /usr/local/php/bin
</VirtualHost>


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