When using PHP as an Apache module, you can also change the configuration settings using directives in Apache configuration files (e.g. httpd.conf) and .htaccess files. You will need "AllowOverride Options" or "AllowOverride All" privileges to do so.
There are several Apache directives that allow you to change the PHP configuration from within the Apache configuration files. For a listing of which directives are PHP_INI_ALL, PHP_INI_PERDIR, or PHP_INI_SYSTEM, have a look at the List of php.ini directives appendix.
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php_valuename value - Sets the value of the specified directive. Can be used only with PHP_INI_ALL and PHP_INI_PERDIR type directives. To clear a previously set value use none as the value.
Note: Don't use
php_valueto set boolean values.php_flag(see below) should be used instead. -
php_flagname on|off - Used to set a boolean configuration directive. Can be used only with PHP_INI_ALL and PHP_INI_PERDIR type directives.
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php_admin_valuename value - Sets the value of the specified directive. This can not be used in .htaccess files. Any directive type set with
php_admin_valuecan not be overridden by .htaccess or ini_set(). To clear a previously set value use none as the value. -
php_admin_flagname on|off - Used to set a boolean configuration directive. This can not be used in .htaccess files. Any directive type set with
php_admin_flagcan not be overridden by .htaccess or ini_set().
Example #1 Apache configuration example
<IfModule mod_php5.c> php_value include_path ".:/usr/local/lib/php" php_admin_flag engine on </IfModule> <IfModule mod_php4.c> php_value include_path ".:/usr/local/lib/php" php_admin_flag engine on </IfModule>
Caution
PHP constants do not exist outside of PHP. For example, in httpd.conf you can not use PHP constants such as E_ALL or E_NOTICE to set the error_reporting directive as they will have no meaning and will evaluate to 0. Use the associated bitmask values instead. These constants can be used in php.ini
Changing PHP configuration via the Windows registry
When running PHP on Windows, the configuration values can be modified on a per-directory basis using the Windows registry. The configuration values are stored in the registry key HKLM\SOFTWARE\PHP\Per Directory Values, in the sub-keys corresponding to the path names. For example, configuration values for the directory c:\inetpub\wwwroot would be stored in the key HKLM\SOFTWARE\PHP\Per Directory Values\c\inetpub\wwwroot. The settings for the directory would be active for any script running from this directory or any subdirectory of it. The values under the key should have the name of the PHP configuration directive and the string value. PHP constants in the values are not parsed. However, only configuration values changeable in PHP_INI_USER can be set this way, PHP_INI_PERDIR values can not.
Other interfaces to PHP
Regardless of how you run PHP, you can change certain values at runtime of your scripts through ini_set(). See the documentation on the ini_set() page for more information.
If you are interested in a complete list of configuration settings on your system with their current values, you can execute the phpinfo() function, and review the resulting page. You can also access the values of individual configuration directives at runtime using ini_get() or get_cfg_var().
Where a configuration setting may be set
add a note User Contributed Notes How to change configuration settings self at pabloviquez dot com 15-Jun-2009 01:07
Note that, changing the PHP configuration via the windows registry will set the new values using php_admin_value. This makes that you cannot override them on runtime.
So for example, if you set the include_path on the windows registry and then you call the set_include_path function in your application, it will return false and won't change the include_path. cawoodm at gmail dot com 04-May-2009 02:41
With IIS it can become confusing that changes to php.ini are ineffective. It seems it is necessary to restart the application pool for the changes to be seen. It would be great if this was not necessary - I am sure I have worked with systems where php.ini changes were immediately effectvie. ravi at syntric dot net 09-Mar-2009 06:52
Just a quick note regarding per-directory php settings. A number of flags can be set custom to a particular app's requirement based on one of two methods describe her http://www.cognitivecombine.com/?p=207
I particularly stumbled upon this to turn off register_globals. Drupal, for e.g., required this to be off but I knew of numerous php apps that had code which relied on these globals. The .htaccess method described in the above URL worked for my case. hyponiq at gmail dot com 09-Feb-2009 05:11
Running PHP under Apache poses a major problem when it comes to per-directory configuration settings for PHP. In Apache virtual hosting, only a master PHP configuration file (i.e. php.ini) is parsed at run-time per PHP script. Under IIS 6.0 or greater, you can include per-directory PHP configuration files to override or overwrite the master configuration settings. The issue here, however, is having Apache virtual hosts override/overwrite master settings; not what IIS can do.
So, there are two possible solutions. The first solution is described in this section and uses the Apache configuration settings php_value, php_flag, php_admin_value, and php_admin_flag. In that, each virtual host which you'd like to have certain configuration settings changed must have these directives set (and that is for each PHP configuration setting). This, to me, is the more viable solution, although it is time-consuming and mentally taxing.
The other possible solution is to set the PHPRC environment variable. To my knowledge, all implementations of Apache HTTPD allow for the SetEnv directive to set the PHPRC variable per-virtual-host. What that does is tell PHP to look in the specified location for that virtual host's configuration settings file (i.e. "C:/path/to/custom/php.ini"). The only downside to this tactic is that EVERY virtual host's custom php.ini file must contain all set parameters. In other words, every single PHP configuration directive you have set in the master php.ini file must ALSO be set in per-virtual-host configuration settings. Doesn't that suck? It seems rather redundant to me (and completely defeats the purpose) that you have to include all configuration settings OVER AND OVER AGAIN.
The great thing about per-directory configuration settings (when they're implemented correctly) is that PHP already has the master settings pre-loaded and the per-directory settings (which may only ammount to one directive in difference) can be loaded per request and, thus, there is less over-head.
There really is more to this topic than that, which is why I blogged a rather lengthy and detailed article here: http://hyponiq.blogspot.com/2009/02/apache-php-multiple-phpini.html This information is meant to help users and administrators. I highly suggest it be read if anyone has any questions on Apache and PHP configurations. I have included some examples that illustrate the two possible solutions, as well. I did my best to research everything before I wrote the article.
I hope this helps!
==== 10-FEB-09: ====
I must add a little more information:
I've done some thorough testing on my PC as to the PHPRC environment variable set by the Apache directive SetEnv. It seems to me that this variable is completely disregarded using that directive. I tried everything and can only come to the conclusion that either A) I did something very wrong, or B) that it simply doesn't work as expected.
The former solution, however, does work magically! So, to expand on my previous post, the only real and viable solution to this problem is to use the php_value, php_flag, php_admin_value and php_admin_flag directives in your virtual hosts configurations.
Once again, it can be very boring! But it does work. ludek dot stepan at gmail dot com 25-Sep-2008 11:37
Hello,
I've found this directive useful for setting per-file php.ini options. For example, when I want to have my .css styles processed as php scripts, I put this code into .htaccess to setup correct mimetype.
AddHandler php5-script .css
<FilesMatch "\.css$">
php_value default_mimetype "text/css"
</FilesMatch>
Yours Ludek contrees.du.reve at gmail dot com 02-Feb-2008 01:25
Being able to put php directives in httpd.conf and have them work on a per-directory or per-vitual host basis is just great. Now there's another aspect which might be worth being aware of:
A php.ini directive put into your apache conf file applies to php when it runs as an apache module (i.e. in a web page), but NOT when it runs as CLI (command-line interface).
Such feature that might be unwanted by an unhappy few, but I guess most will find it useful. As far as I'm concerned, I'm really happy that I can use open_basedir in my httpd.conf file, and it restricts the access of web users and sub-admins of my domain, but it does NOT restrict my own command-line php scripts... webmaster at htaccesselite dot com 12-Jul-2007 03:18
To change the configuration for php running as cgi those handy module commands won't work.. The work-around is being able to tell php to start with a custom php.ini file.. configured the way you want.
With multiple custom php.ini files
-------------------------------------------
/site/ini/1/php.ini
/site/ini/2/php.ini
/site/ini/3/php.ini
--
The trick is creating a wrapper script to set the location of the php.ini file that php will use. Then it exec's the php cgi.
shell script /cgi-bin/phpini.cgi
-------------------------------------------
#!/bin/sh
export PHPRC=/site/ini/1
exec /cgi-bin/php5.cgi
--
Now all you have to do is setup Apache to run php files through the wrapper script instead of just executing the php cgi.
In your .htaccess or httpd.conf file
-------------------------------------------
AddHandler php-cgi .php
Action php-cgi /cgi-bin/phpini.cgi
--
So to change the configuration of php you just need to change the PHPRC variable to point to a different directory containing your customized php.ini.. You could also create multiple shell wrapper scripts and create multiple Handler's+Actions in .htaccess..
in your .htaccess
-------------------------------------------
AddHandler php-cgi1 .php1
Action php-cgi1 /cgi-bin/phpini-1.cgi
AddHandler php-cgi2 .php2
Action php-cgi2 /cgi-bin/phpini-2.cgi
AddHandler php-cgi3 .php3
Action php-cgi3 /cgi-bin/phpini-3.cgi
--
The only caveat here is that it seems like you would have to rename the file extensions, but there are ways around that too ->
http://www.askapache.com/php/custom-phpini-tips-and-tricks.html Woody/mC 09-Jul-2007 01:09
@ pgl: As the documentation says:
"To clear a previously set value use none as the value."
Works fine for me. pgl at yoyo dot org 27-Jun-2007 10:59
It is not possible to unset a config option using php_value. This caused me problems with auto_prepend_file settings where I wanted to have a global file auto included, with an exception for only one site. The solution used to be to use auto_prepend_file /dev/null, but this now causes errors, so I just create and include blank.inc now instead. 
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