In PHP what is the right approach for loading configuration parameters into application variables?

Question

I have a database where I keep my configuration parameters, I want to load the configuration parameters into my application variables only once (or upon specific request to reload the parameters), I also want these variables which holds the configuration parameters to be accessible from all php pages/scripts, the idea is to save hits on the database and improve the application response time. What is the 'classic' php solution to this matter?

Answer 1

Make a page that sets constants (key word 'define') early in your routines. Just include it wherever needed.

Answer 2

It seems to me that this is essentially the same as any other caching question. The fact that the content to be cached is configuration parameters rather than say the content of Web pages or user profile information is unimportant from a technical perspective.

So what you have to do is come up with some caching solution, whether it's memcached or just writing static files with the data you want to cache.

The trick here is that you're not caching HTML to be presented to the user but rather database query results, so you'll probably want to look at approaches like this one:

http://devzone.zend.com/article/1258

Answer 3

Like Smandoli's answer, I use a single file that has my configuration.

However, my configuration is actually a multi-dimensional array - meaning I have much greater control over my config - I can change it on the fly if I need to, as well as breaking up the varialbes.

$config['error']['nologin'] = "You're not logged in";
$config['db']['host'] = "localhost";
$config['something']['else'] = "hello world";

Edit: I use a file for values that do not change too much. I do use variables from a database occasionally, but not too often.

My rule of thumb is "If the user doesn't need to change it, load from the file; if they need to change it, then it comes from a database".

Answer 4

I like using the Zend_Config_Ini class. Creating separate sections that can extend others is easy, and with Zend_Cache with Zend_Cache_Frontend_File (to check for updates to the .ini file) and a backend (I use APC) that is particularly fast to access to avoid any overhead of re-parsing.

; Production site configuration data
[production]
webhost                  = www.example.com
database.adapter         = pdo_mysql
database.params.host     = db.example.com
database.params.username = dbuser
database.params.password = secret
database.params.dbname   = dbname

; Staging site configuration data inherits from production and
; overrides values as necessary
[staging : production]
;  'database.adapter' is inherited
;  others are overridden
database.params.host     = dev.example.com
database.params.username = devuser
database.params.password = devsecret

Answer 5

I came from the world of C++ the paradigm there was to use a singleton which load the parameters on first (and only) instantiation and export an interface with relevant get'ters (like 'int GetVal(char* key,int &val)' ) the singletone was accessible from all parts of the application, is there anything like that in PHP?