Does enabling the configuration option with-config-file-scan-dir when compiling PHP lead to performance issues?
Specifically, does this tell the PHP binary to do a file system scan every time the PHP module is loaded to respond to a request?
I imagine it does, and that having multiple ini files causes just a little more disk access on every request. I suppose this could be mitigated by placing all those separate directives into the same php.ini file.
Can anyone confirm or deny this?
No, If I understand it correctly you will provide it a directory which when the PHP config is loaded (at apache startup) PHP will read every file in the directory as a config file.
Does this tell the PHP binary to do a file system scan every time the PHP module is loaded to respond to a request?
No. When you compile --with-config-file-scan-dir=/path/to/dir all you're doing is telling PHP combine all files in this directory into its configuration. This is a method often used in system configuration where package management systems need to be able to add/remove package specific configuration from an application without potentially destroying a end-user modified config file. An example here would be, on a Debian based system, when you apt-get install php-pgsql, it will create a /etc/php/conf.d/pgsql.ini which will contain the extension=pgsql.so line, as well as any module-specific options.
Does enabling the configuration option with-config-file-scan-dir when compiling PHP lead to performance issues?
Not really. In practice, it is simply a concatenation of all the .ini files in that particular directory.
I can tell you that Debian, CentOS, and Zend Server all use this option by default.
Also, just off the top of my head, *nix RC files, Apache2, Courier, Emacs, and Cron all use (or can use) similar approaches to loading configurations.
Bryan,
The CLI/(Fast)CGI versions do load the .ini files each time they are fired up; however, the apache module loads them once into memory when the server is started. You can test this behavior by changing a value in any of the .ini files and running the CLI binary. Notice that you need a server restart before you can see the changes in the server module version.