Selecting and downloading the PHP distribution package

Download the PHP zip binary distribution from » PHP for Windows: Binaries and Sources. There are several different versions of the zip package - to choose the right version for you, follow the detailed guide on the » download page.

The PHP package structure and content

Unpack the content of the zip archive into a directory of your choice, for example C:\PHP\. The directory and file structure extracted from the zip will look as below:

c:\php
   |
   +--dev
   |  |
   |  |-php5ts.lib                 -- php5.lib in non thread safe version
   |
   +--ext                          -- extension DLLs for PHP
   |  |
   |  |-php_bz2.dll
   |  |
   |  |-php_cpdf.dll
   |  |
   |  |-...
   |
   +--extras                       -- empty 
   |
   +--pear                         -- initial copy of PEAR
   |
   |
   |-go-pear.bat                   -- PEAR setup script
   |
   |-...
   |
   |-php-cgi.exe                   -- CGI executable
   |
   |-php-win.exe                   -- executes scripts without an opened command prompt
   |
   |-php.exe                       -- Command line PHP executable (CLI)
   |
   |-...
   |
   |-php.ini-development           -- default php.ini settings
   |
   |-php.ini-production            -- recommended php.ini settings
   |
   |-php5apache2_2.dll             -- does not exist in non thread safe version
   |
   |-php5apache2_2_filter.dll      -- does not exist in non thread safe version
   |
   |-...
   |
   |-php5ts.dll                    -- core PHP DLL ( php5.dll in non thread safe version)
   | 
   |-...

Below is the list of the modules and executables included in the PHP zip distribution:

• go-pear.bat - the PEAR setup script. Refer to » Installation (PEAR) for more details.

• php-cgi.exe - CGI executable that can be used when running PHP on IIS via CGI or FastCGI.

• php-win.exe - the PHP executable for executing PHP scripts without using a command line window (for example PHP applications that use Windows GUI).

• php.exe - the PHP executable for executing PHP scripts within a command line interface (CLI).

• php5apache2_2.dll - Apache 2.2.X module.

• php5apache2_2_filter.dll - Apache 2.2.X filter.

Changing the php.ini file

After the php package content has been extracted, copy the php.ini-production into php.ini in the same folder. If necessary, it is also possible to place the php.ini into any other location of your choice but that will require additional configuration steps as described in PHP Configuration.

The php.ini file tells PHP how to configure itself, and how to work with the environment that it runs in. Here are a number of settings for the php.ini file that help PHP work better with Windows. Some of these are optional. There are many other directives that may be relevant to your environment - refer to the list of php.ini directives for more information.

Required directives:

• extension_dir = <path to extension directory> - The extension_dir needs to point to the directory where PHP extensions files are stored. The path can be absolute (i.e. "C:\PHP\ext") or relative (i.e. ".\ext"). Extensions that are listed lower in the php.ini file need to be located in the extension_dir.

• extension = xxxxx.dll - For each extension you wish to enable, you need a corresponding "extension=" directive that tells PHP which extensions in the extension_dir to load at startup time.

• log_errors = On - PHP has an error logging facility that can be used to send errors to a file, or to a service (i.e. syslog) and works in conjunction with the error_log directive below. When running under IIS, the log_errors should be enabled, with a valid error_log.

• error_log = <path to the error log file> - The error_log needs to specify the absolute, or relative path to the file where PHP errors should be logged. This file needs to be writable for the web server. The most common places for this file are in various TEMP directories, for example "C:\inetpub\temp\php-errors.log".

• cgi.force_redirect = 0 - This directive is required for running under IIS. It is a directory security facility required by many other web servers. However, enabling it under IIS will cause the PHP engine to fail on Windows.

• cgi.fix_pathinfo = 1 - This lets PHP access real path info following the CGI Spec. The IIS FastCGI implementation needs this set.

• fastcgi.impersonate = 1 - FastCGI under IIS supports the ability to impersonate security tokens of the calling client. This allows IIS to define the security context that the request runs under.

• fastcgi.logging = 0 - FastCGI logging should be disabled on IIS. If it is left enabled, then any messages of any class are treated by FastCGI as error conditions which will cause IIS to generate an HTTP 500 exception.

Optional directives

• max_execution_time = ## - This directive tells PHP the maximum amount of time that it can spend executing any given script. The default for this is 30 seconds. Increase the value of this directive if PHP application take long time to execute.

• memory_limit = ###M - The amount of memory available for the PHP process, in Megabytes. The default is 128, which is fine for most PHP applications. Some of the more complex ones might need more.

• display_errors = Off - This directive tells PHP whether to include any error messages in the stream that it returns to the Web server. If this is set to "On", then PHP will send whichever classes of errors that you define with the error_reporting directive back to web server as part of the error stream. For security reasons it is recommended to set it to "Off" on production servers in order not to reveal any security sensitive information that is often included in the error messages.

• open_basedir = <paths to directories, separated by semicolon>, e.g. openbasedir="C:\inetpub\wwwroot;C:\inetpub\temp". This directive specified the directory paths where PHP is allowed to perform file system operations. Any file operation outside of the specified paths will result in an error. This directive is especially useful for locking down the PHP installation in shared hosting environments to prevent PHP scripts from accessing any files outside of the web site's root directory.

• upload_max_filesize = ###M and post_max_size = ###M - The maximum allowed size of an uploaded file and post data respectively. The values of these directives should be increased if PHP applications need to perform large uploads, such as for example photos or video files.

PHP is now setup on your system. The next step is to choose a web server, and enable it to run PHP. Choose a web server from the table of contents.

In addition to running PHP via a web server, PHP can run from the command line just like a .BAT script. See

Configuring IIS to process PHP requests

Download and install PHP in accordance to the instructions described in manual installation steps

Note:

Non-thread-safe build of PHP is recommended when using IIS. The non-thread-safe builds are available at » PHP for Windows: Binaries and Sources Releases.

Configure the CGI- and FastCGI-specific settings in php.ini file as shown below:

fastcgi.impersonate = 1
fastcgi.logging = 0
cgi.fix_pathinfo=1
cgi.force_redirect = 0

Download and install the » Microsoft FastCGI Extension for IIS 5.1 and 6.0. The extension is available for 32-bit and 64-bit platforms - select the right download package for your platform.

Configure the FastCGI extension to handle PHP-specific requests by running the command shown below. Replace the value of the "-path" parameter with the absolute file path to the php-cgi.exe file.

cscript %windir%\system32\inetsrv\fcgiconfig.js -add -section:"PHP" ^
-extension:php -path:"C:\PHP\php-cgi.exe"

This command will create an IIS script mapping for *.php file extension, which will result in all URLs that end with .php being handled by FastCGI extension. Also, it will configure FastCGI extension to use the executable php-cgi.exe to process the PHP requests.

Note:

At this point the required installation and configuration steps are completed. The remaining instructions below are optional but highly recommended for achieving optimal functionality and performance of PHP on IIS.

Impersonation and file system access

It is recommended to enable FastCGI impersonation in PHP when using IIS. This is controlled by the fastcgi.impersonate directive in php.ini file. When impersonation is enabled, PHP will perform all the file system operations on behalf of the user account that has been determined by IIS authentication. This ensures that even if the same PHP process is shared across different IIS web sites, the PHP scripts in those web sites will not be able to access each others' files as long as different user accounts are used for IIS authentication on each web site.

For example IIS 5.1 and IIS 6.0, in its default configuration, has anonymous authentication enabled with built-in user account IUSR_<MACHINE_NAME> used as a default identity. This means that in order for IIS to execute PHP scripts, it is necessary to grant IUSR_<MACHINE_NAME> account read permission on those scripts. If PHP applications need to perform write operations on certain files or write files into some folders then IUSR_<MACHINE_NAME> account should have write permission to those.

To determine which user account is used by IIS anonymous authentication, follow these steps:

To modify the permissions settings on files and folders, use the Windows Explorer user interface or icacls command.

icacls C:\inetpub\wwwroot\upload /grant IUSR:(OI)(CI)(M)

Set index.php as a default document in IIS

The IIS default documents are used for HTTP requests that do not specify a document name. With PHP applications, index.php usually acts as a default document. To add index.php to the list of IIS default documents, follow these steps:

FastCGI and PHP Recycling configuration

Configure IIS FastCGI extension settings for recycling of PHP processes by using the commands shown below. The FastCGI setting instanceMaxRequests controls how many requests will be processed by a single php-cgi.exe process before FastCGI extension shuts it down. The PHP environment variable PHP_FCGI_MAX_REQUESTS controls how many requests a single php-cgi.exe process will handle before it recycles itself. Make sure that the value specified for FastCGI InstanceMaxRequests setting is less than or equal to the value specified for PHP_FCGI_MAX_REQUESTS.

cscript %windir%\system32\inetsrv\fcgiconfig.js -set -section:"PHP" ^
-InstanceMaxRequests:10000

cscript %windir%\system32\inetsrv\fcgiconfig.js -set -section:"PHP" ^
-EnvironmentVars:PHP_FCGI_MAX_REQUESTS:10000

Configuring FastCGI timeout settings

Increase the timeout settings for FastCGI extension if there are applications that have long running PHP scripts. The two settings that control timeouts are ActivityTimeout and RequestTimeout. Refer to » Configuring FastCGI Extension for IIS 6.0 for more information about those settings.

cscript %windir%\system32\inetsrv\fcgiconfig.js -set -section:"PHP" ^
-ActivityTimeout:90

cscript %windir%\system32\inetsrv\fcgiconfig.js -set -section:"PHP" ^
-RequestTimeout:90

Changing the Location of php.ini file

PHP searches for php.ini file in several locations and it is possible to change the default locations of php.ini file by using PHPRC environment variable. To instruct PHP to load the configuration file from a custom location run the command shown below. The absolute path to the directory with php.ini file should be specified as a value of PHPRC environment variable.

cscript %windir%\system32\inetsrv\fcgiconfig.js -set -section:"PHP" ^
-EnvironmentVars:PHPRC:"C:\Some\Directory\"

Enabling FastCGI support in IIS

FastCGI module is disabled in default installation of IIS. The steps to enable it differ based on the version of Windows being used.

To enable FastCGI support on Windows Vista SP1 and Windows 7:

To enable FastCGI support on Windows Server 2008 and Windows Server 2008 R2:

Configuring IIS to process PHP requests

Download and install PHP in accordance to the instructions described in manual installation steps

Note:

Non-thread-safe build of PHP is recommended when using IIS. The non-thread-safe builds are available at » PHP for Windows: Binaries and Sources Releases.

Configure the CGI- and FastCGI-specific settings in php.ini file as shown below:

fastcgi.impersonate = 1
fastcgi.logging = 0
cgi.fix_pathinfo=1
cgi.force_redirect = 0

Configure IIS handler mapping for PHP by using either IIS Manager user interface or a command line tool.

Using IIS Manager user interface to create a handler mapping for PHP

Follow these steps to create an IIS handler mapping for PHP in IIS Manager user interface:

1. In the Windows Start Menu choose "Run:", type "inetmgr" and click "Ok";

2. In the IIS Manager user interface select the server node in the "Connections" tree view;

3. In the "Features View" page open the "Handler Mappings" feature;

   

4. In the "Actions" pane click "Add Module Mapping...";

5. In the "Add Module Mapping" dialog enter the following:

   • Request path: *.php
   • Module: FastCgiModule
   • Executable: C:\[Path to PHP installation]\php-cgi.exe
   • Name: PHP_via_FastCGI

6. Click "Request Restrictions" button and then configure the mapping to invoke handler only if request is mapped to a file or a folder;

7. Click OK on all the dialogs to save the configuration.

%windir%\system32\inetsrv\appcmd set config /section:system.webServer/fastCGI ^
/+[fullPath='c:\PHP\php-cgi.exe']

%windir%\system32\inetsrv\appcmd set config /section:system.webServer/handlers ^
/+[name='PHP_via_FastCGI', path='*.php',verb='*',modules='FastCgiModule',^
scriptProcessor='c:\PHP\php-cgi.exe',resourceType='Either']

Impersonation and file system access

It is recommended to enable FastCGI impersonation in PHP when using IIS. This is controlled by the fastcgi.impersonate directive in php.ini file. When impersonation is enabled, PHP will perform all the file system operations on behalf of the user account that has been determined by IIS authentication. This ensures that even if the same PHP process is shared across different IIS web sites, the PHP scripts in those web sites will not be able to access each other's files as long as different user accounts are used for IIS authentication on each web site.

For example IIS 7, in its default configuration, has anonymous authentication enabled with built-in user account IUSR used as a default identity. This means that in order for IIS to execute PHP scripts, it is necessary to grant IUSR account read permission on those scripts. If PHP applications need to perform write operations on certain files or write files into some folders then IUSR account should have write permission to those.

To determine what user account is used as an anonymous identity in IIS 7 use the following command. Replace the "Default Web Site" with the name of IIS web site that you use. In the output XML configuration element look for the userName attribute.

%windir%\system32\inetsrv\appcmd.exe list config "Default Web Site" ^
/section:anonymousAuthentication

<system.webServer>
  <security>
    <authentication>
      <anonymousAuthentication enabled="true" userName="IUSR" />
    </authentication>
   </security>
</system.webServer>

Note:

If userName attribute is not present in the anonymousAuthentication element, or is set to an empty string, then it means that the application pool identity is used as an anonymous identity for that web site.

To modify the permissions settings on files and folders, use the Windows Explorer user interface or icacls command.

icacls C:\inetpub\wwwroot\upload /grant IUSR:(OI)(CI)(M)

Set index.php as a default document in IIS

The IIS default documents are used for HTTP requests that do not specify a document name. With PHP applications, index.php usually acts as a default document. To add index.php to the list of IIS default documents, use this command:

%windir%\system32\inetsrv\appcmd.exe set config ^
-section:system.webServer/defaultDocument /+"files.[value='index.php']" ^
/commit:apphost

FastCGI and PHP Recycling configuration

Configure IIS FastCGI settings for recycling of PHP processes by using the commands shown below. The FastCGI setting instanceMaxRequests controls how many requests will be processed by a single php-cgi.exe process before IIS shuts it down. The PHP environment variable PHP_FCGI_MAX_REQUESTS controls how many requests a single php-cgi.exe process will handle before it recycles itself. Make sure that the value specified for FastCGI InstanceMaxRequests setting is less than or equal to the value specified for PHP_FCGI_MAX_REQUESTS.

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/fastCgi ^
/[fullPath='c:\php\php-cgi.exe'].instanceMaxRequests:10000

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/fastCgi ^
/+"[fullPath='C:\{php_folder}\php-cgi.exe'].environmentVariables.^
[name='PHP_FCGI_MAX_REQUESTS',value='10000']"

FastCGI timeout settings

Increase the timeout settings for FastCGI if it is expected to have long running PHP scripts. The two settings that control timeouts are activityTimeout and requestTimeout. Use the commands below to change the timeout settings. Make sure to replace the value in the fullPath parameter to contain the absolute path to the php-cgi.exe file.

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/fastCgi ^
/[fullPath='C:\php\php-cgi.exe',arguments=''].activityTimeout:"90"  /commit:apphost

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/fastCgi ^
/[fullPath='C:\php\php-cgi.exe',arguments=''].requestTimeout:"90"  /commit:apphost

Changing the Location of php.ini file

PHP searches for php.ini file in several locations and it is possible to change the default locations of php.ini file by using PHPRC environment variable. To instruct PHP to load the configuration file from a custom location run the command shown below. The absolute path to the directory with php.ini file should be specified as a value of PHPRC environment variable.

appcmd.exe set config  -section:system.webServer/fastCgi ^
/+"[fullPath='C:\php\php.exe',arguments=''].environmentVariables.^
[name='PHPRC',value='C:\Some\Directory\']" /commit:apphost

Installing as an Apache module

You should add the following lines to your Apache httpd.conf file:

# Add to the end of the LoadModule section
# Don't forget to copy this file from the sapi directory!
LoadModule php4_module "C:/php/php4apache.dll"

# Add to the end of the AddModule section
AddModule mod_php4.c

# Add to the end of the LoadModule section
LoadModule php5_module "C:/php/php5apache.dll"

# Add to the end of the AddModule section
AddModule mod_php5.c

# Add this line inside the <IfModule mod_mime.c> conditional brace
AddType application/x-httpd-php .php

# For syntax highlighted .phps files, also add
AddType application/x-httpd-php-source .phps

Installing as a CGI binary

If you unzipped the PHP package to C:\php\ as described in the Manual Installation Steps section, you need to insert these lines to your Apache configuration file to set up the CGI binary:

ScriptAlias /php/ "c:/php/"
AddType application/x-httpd-php .php

# For PHP 4
Action application/x-httpd-php "/php/php.exe"

# For PHP 5
Action application/x-httpd-php "/php/php-cgi.exe"

# specify the directory where php.ini is
SetEnv PHPRC C:/php

If you would like to present PHP source files syntax highlighted, there is no such convenient option as with the module version of PHP. If you chose to configure Apache to use PHP as a CGI binary, you will need to use the highlight_file function. To do this simply create a PHP script file and add this code: <?php highlight_file('some_php_script.php'); ?>.

Installing as an Apache handler

You need to insert the following lines into your Apache httpd.conf configuration file to load the PHP module for Apache 2.x:

# 
LoadModule php5_module "c:/php/php5apache2.dll"
AddHandler application/x-httpd-php .php

# configure the path to php.ini
PHPIniDir "C:/php"

Note: Remember to substitute your actual path to PHP for the C:/php/ in the above examples. Take care to use either php5apache2.dll or php5apache2_2.dll in your LoadModule directive and verify that the referenced file is in fact located at the file path that you point to in this directive.

The above configuration will enable PHP handling of any file that has a .php extension, even if there are other file extensions. For example, a file named example.php.txt will be executed by the PHP handler. To ensure that only files that end in .php are executed, use the following configuration instead:

<FilesMatch \.php$>
      SetHandler application/x-httpd-php
 </FilesMatch>

Running PHP as CGI

You should consult the » Apache CGI documentation for a more complete understanding of running CGI on Apache.

To run PHP as CGI, you'll need to place your php-cgi files in a directory designated as a CGI directory using the ScriptAlias directive.

You will then need to insert a #! line in the PHP files, pointing to the location of your PHP binary:

#!C:/php/php.exe
<?php
  phpinfo();
?>

Running PHP under FastCGI

Running PHP under FastCGI has a number of advantages over running it as a CGI. Setting it up this way is fairly straightforward:

Obtain mod_fcgid from » http://httpd.apache.org/mod_fcgid/. Win32 binaries are available for download from that site. Install the module according to the instructions that will come with it.

Configure your web server as shown below, taking care to adjust any paths to reflect your how you have installed things on your particular system:

LoadModule fcgid_module modules/mod_fcgid.so  

# Where is your php.ini file?
FcgidInitialEnv PHPRC        "c:/php" 

AddHandler fcgid-script .php  
FcgidWrapper "c:/php/php-cgi.exe" .php  

CGI setup on Sun, iPlanet and Netscape servers

To install PHP as a CGI handler, do the following:

• Copy php4ts.dll to your systemroot (the directory where you installed Windows)

• Make a file association from the command line. Type the following two lines:

  assoc .php=PHPScript
  ftype PHPScript=c:\php\php.exe %1 %*

• In the Netscape Enterprise Administration Server create a dummy shellcgi directory and remove it just after (this step creates 5 important lines in obj.conf and allow the web server to handle shellcgi scripts).
• In the Netscape Enterprise Administration Server create a new mime type (Category: type, Content-Type: magnus-internal/shellcgi, File Suffix:php).
• Do it for each web server instance you want PHP to run

More details about setting up PHP as a CGI executable can be found here: » http://benoit.noss.free.fr/php/install-php.html

NSAPI setup on Sun, iPlanet and Netscape servers

To install PHP with NSAPI, do the following:

• Copy php4ts.dll to your systemroot (the directory where you installed Windows)

• Make a file association from the command line. Type the following two lines:

  assoc .php=PHPScript
  ftype PHPScript=c:\php\php.exe %1 %*

• In the Netscape Enterprise Administration Server create a new mime type (Category: type, Content-Type: magnus-internal/x-httpd-php, File Suffix: php).

• Edit magnus.conf (for servers >= 6) or obj.conf (for servers < 6) and add the following: You should place the lines after mime types init.

  Init fn="load-modules" funcs="php4_init,php4_execute,php4_auth_trans" shlib="c:/php/sapi/php4nsapi.dll"
  Init fn="php4_init" LateInit="yes" errorString="Failed to initialise PHP!" [php_ini="c:/path/to/php.ini"]
  

  (PHP >= 4.3.3) The php_ini parameter is optional but with it you can place your php.ini in your web server configuration directory.

• Configure the default object in obj.conf (for virtual server classes [Sun Web Server 6.0+] in their vserver.obj.conf): In the <Object name="default"> section, place this line necessarily after all 'ObjectType' and before all 'AddLog' lines:

  Service fn="php4_execute" type="magnus-internal/x-httpd-php" [inikey=value inikey=value ...]
  

  (PHP >= 4.3.3) As additional parameters you can add some special php.ini-values, for example you can set a docroot="/path/to/docroot" specific to the context php4_execute is called. For boolean ini-keys please use 0/1 as value, not "On","Off",... (this will not work correctly), e.g. zlib.output_compression=1 instead of zlib.output_compression="On"

• This is only needed if you want to configure a directory that only consists of PHP scripts (same like a cgi-bin directory):

  <Object name="x-httpd-php">
  ObjectType fn="force-type" type="magnus-internal/x-httpd-php"
  Service fn=php4_execute [inikey=value inikey=value ...]
  </Object>
  

  After that you can configure a directory in the Administration server and assign it the style x-httpd-php. All files in it will get executed as PHP. This is nice to hide PHP usage by renaming files to .html.

• Restart your web service and apply changes
• Do it for each web server instance you want PHP to run

Note:

More details about setting up PHP as an NSAPI filter can be found here: » http://benoit.noss.free.fr/php/install-php4.html

Note:

The stacksize that PHP uses depends on the configuration of the web server. If you get crashes with very large PHP scripts, it is recommended to raise it with the Admin Server (in the section "MAGNUS EDITOR").

CGI environment and recommended modifications in php.ini

Important when writing PHP scripts is the fact that Sun JSWS/Sun ONE WS/iPlanet/Netscape is a multithreaded web server. Because of that all requests are running in the same process space (the space of the web server itself) and this space has only one environment. If you want to get CGI variables like PATH_INFO, HTTP_HOST etc. it is not the correct way to try this in the old PHP way with getenv or a similar way (register globals to environment, $_ENV). You would only get the environment of the running web server without any valid CGI variables!

Note:

Why are there (invalid) CGI variables in the environment?

Answer: This is because you started the web server process from the admin server which runs the startup script of the web server, you wanted to start, as a CGI script (a CGI script inside of the admin server!). This is why the environment of the started web server has some CGI environment variables in it. You can test this by starting the web server not from the administration server. Use the command line as root user and start it manually - you will see there are no CGI-like environment variables.

Simply change your scripts to get CGI variables in the correct way for PHP 4.x by using the superglobal $_SERVER. If you have older scripts which use $HTTP_HOST, etc., you should turn on register_globals in php.ini and change the variable order too (important: remove "E" from it, because you do not need the environment here):

variables_order = "GPCS"
register_globals = On

Special use for error pages or self-made directory listings (PHP >= 4.3.3)

You can use PHP to generate the error pages for "404 Not Found" or similar. Add the following line to the object in obj.conf for every error page you want to overwrite:

Error fn="php4_execute" code=XXX script="/path/to/script.php" [inikey=value inikey=value...]

Another possibility is to generate self-made directory listings. Just create a PHP script which displays a directory listing and replace the corresponding default Service line for type="magnus-internal/directory" in obj.conf with the following:

Service fn="php4_execute" type="magnus-internal/directory" script="/path/to/script.php" [inikey=value inikey=value...]

Note about nsapi_virtual and subrequests (PHP >= 4.3.3)

The NSAPI module now supports the nsapi_virtual function (alias: virtual) to make subrequests on the web server and insert the result in the web page. The problem is, that this function uses some undocumented features from the NSAPI library.

Under Unix this is not a problem, because the module automatically looks for the needed functions and uses them if available. If not, nsapi_virtual is disabled.

Under Windows limitations in the DLL handling need the use of a automatic detection of the most recent ns-httpdXX.dll file. This is tested for servers till version 6.1. If a newer version of the Sun server is used, the detection fails and nsapi_virtual is disabled.

If this is the case, try the following: Add the following parameter to php4_init in magnus.conf/obj.conf:

Init fn=php4_init ... server_lib="ns-httpdXX.dll"

You can check the status by using the phpinfo function.

Note:

But be warned: Support for nsapi_virtual is EXPERIMENTAL!!!