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I want to have a constant (a string) that is available to all PHP-scripts on the server.

According to http://php.net/manual/en/function.parse-ini-file.php this is quite easy if you parse an extra .ini file, however I don't want to parse an extra file, I want to set my constant in the global php.ini without having to parse anything in the scripts. (In fact that's the whole point because I need the constant to find the stuff to include/parse/etc: When I know where this extra .ini file would be, I don't need it anymore!)

Just inventing a new constant in php.ini and then trying to access it with ini_get() does not work, is there any other way?

I compile Apache and PHP myself, so I could also set the constant at compile-time and/or use Apache-constants if that is neccessary.

Robby75
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3 Answers3

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You can use a PHP auto_prepend_file script in your PHP ini to do this as it will be run before any of your user-land scripts:

Specifies the name of a file that is automatically parsed before the main file. The file is included as if it was called with the require function, so include_path is used.

So you can add an ini line like:

auto_prepend_file="/home/user/script.php"

The in /home/user/script.php:

define('CONSTANT_NAME', 'your nice value here');

Now in your PHP scripts you can access CONSTANT_NAME from wherever you like as it is available in all PHP scripts.

I use this technique on my staging server that uses mod_rewrite based mass virtual hosting so I can give my PHP scripts an accurate document root. I have discussed this in a blog post before.

Treffynnon
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Simple. Create a file xxx.php where you define your constant and add that file to the global include_path in php.ini. I would like to add though that keeping this kind of global constants or variables is not a recommended way of working as you may forget where are the constants coming from and is not making your apps very portable and explicit to other developers.

Elzo Valugi
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From what you've said I think you'll find that there will already be something similar already available in $_SERVER, in particular 'DOCUMENT_ROOT'.

Rob Forrest
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  • Exactly, I need something very similar to DOCUMENT_ROOT (but not DOCUMENT_ROOT, which is the whole point of this question) – Robby75 May 25 '12 at 09:27
  • @Robby75 that is exactly what I am using the solution in my answer to achieve on my staging server: http://stackoverflow.com/a/10751734/461813 – Treffynnon May 25 '12 at 09:31