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# How to change configuration settings

## Running PHP as an Apache module

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.

With PHP 4 and PHP 5, 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.

> Note: With PHP 3, there are Apache directives that correspond to each configuration setting in the `php3.ini` name, except the name is prefixed by "php3_".

php_value name 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_value to set boolean values. php_flag (see below) should be used instead.

php_flag name on|off

  Used to set a boolean configuration directive. Can be used only with `PHP_INI_ALL` and `PHP_INI_PERDIR` type directives.

php_admin_value name value

  Sets the value of the specified directive. This can not be used in `.htaccess` files. Any directive type set with php_admin_value can not be overridden by `.htaccess` or virtualhost directives. To clear a previously set value use none as the value.

php_admin_flag name on|off

  Used to set a boolean configuration directive. This can not be used in `.htaccess` files. Any directive type set with php_admin_flag can not be overridden by `.htaccess` or virtualhost directives.

Example 9-2. Apache configuration example
    <IfModule mod_php5.c>
      php_value include_path ".:/usr/local/lib/php"
      php_admin_flag safe_mode on
    </IfModule>
    <IfModule mod_php4.c>
      php_value include_path ".:/usr/local/lib/php"
      php_admin_flag safe_mode on
    </IfModule>
    <IfModule mod_php3.c>
      php3_include_path ".:/usr/local/lib/php"
      php3_safe_mode 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().

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