virtual

(PHP 4, PHP 5, PHP 7, PHP 8)

virtual — Perform an Apache sub-request

Description

virtual(string $uri): bool

virtual() is an Apache-specific function which is similar to  in mod_include. It performs an Apache sub-request. It is useful for including CGI scripts or .shtml files, or anything else that you would parse through Apache. Note that for a CGI script, the script must generate valid CGI headers. At the minimum that means it must generate a Content-Type header.

To run the sub-request, all buffers are terminated and flushed to the browser, pending headers are sent too.

This function is supported when PHP is installed as an Apache module webserver.

Parameters

uri: The file that the virtual command will be performed on.

Return Values

Performs the virtual command on success, or returns false on failure.

Examples

See apache_note() for an example.

Notes

Warning

The query string can be passed to the included file but $_GET is copied from the parent script and only $_SERVER['QUERY_STRING'] is filled with the passed query string. The query string may only be passed when using Apache 2. The requested file will not be listed in the Apache access log.

Note:
Environment variables set in the requested file are not visible to the calling script.

Note:
This function may be used on PHP files. However, it is typically better to use include or require for PHP files.

Found A Problem?

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 14 notes

down

php at nagler-ihlein dot de ¶

4 years ago

Starting with 7.2 various session related things were changed and it seems part of it is conflicting with virtual(). Calling it you may receive a "PHP Warning:  virtual(): Headers already sent. You cannot change the session module's ini settings at this time in ..." although no header was set and virtual() should simply provide static content from a file.

It took half a day to find out that some main session.configuration.php settings (e.g. save_handler, serialize_handler, or save_path) in the Apache config (all levels) are causing this. It seems the settings are regarded as likely to change headers but virtual() is already beyond sending them. Unfortunately the warning is then not only logged to error_log but also part of the content virtual() sends to the client which screws it up - the format of the content like binary image data is no more correct.

If you do not need php's session management you can remove all session.* settings in your apache configuration to avoid the warning. Otherwise a workaround is to switch off E_WARNING before calling virtual().

<?php
$filename = '/data/image.jpg';
$level = error_reporting();
error_reporting($level & ~E_WARNING); 
virtual($filename);
error_reporting($level);
?>

down

crazyted at crazyted dot com ¶

22 years ago

I have a header that's include()'ed on each of my pages. I then wanted to add a Perl script to that header file (header.php) via the virtual() command. 

Since my header is used by documents in my /www folder along with other folders inside that (and inside those), and virtual() seems to take only relative paths, I had to write some code to dynamically get the path to the perl script.

Hope this helps some ppl out:

  $cwd = getcwd();
  $script_name = "cgi-bin/perl_script.pl";
  $count = substr_count($cwd, '/');
  $count = $count - 3;
  // get rid of extra absolute paths since my directory is /home/user/www

  // Add additional path information
  for($i = 1; $i <= $count; $i++){
    $script_name = "../".$script_name;      
  }
  virtual($script_name);

down

vcaron at bearstech dot com ¶

18 years ago

You can use virtual() to implement your own dispatcher/auth handler in an efficient and effective way.

For instance if you have a bunch of images you would like to be served statically by Apache (its job after all), but with a more com
plex access pattern than mod_access allows you to do (say a MySQL lookup with your app logic), try this simple Apache rule:

  Order Allow,Deny
  Allow from env=PHP_ALLOW

Then in your PHP script, before sending any content or header:

<?php
$image = "/some/URL/path/test.png";
if (client_may_view_image($image)) {
  apache_setenv('PHP_ALLOW', '1');
  if (virtual($image))
    exit(0);
  echo "Ops, failed to fetched granted image $image (hammer your webmaster).\n";
} else
  echo "Sorry buddy, you're not allowed in here.\n";
?>

Of course very Apache-ish, but it's much more efficient and uniform to rely on Apache rather than passthru() and mime_content_type()
 hacks : it does the path lookup and auth/security audit as the admin expects, use the best static serving it can (think 'sendfile')
 and you can even chain your request with another embedded script eg. in mod_perl.

down

Peter Kehl ¶

11 years ago

This documentation is not clear enough. Parameter $filename is not a filename as on the filesystem, but a URI. It can be absolute, starting with /, or relative to URI that involved the PHP script which called virtual(). (I.e. if the PHP script that calls virtual() is invoked via PHP require/require_once/include/include_once mechanism and it passes a relative URI to virtual(), then that URI must be relative to the URI of the topmost PHP script on the inclusion stack.)

Not sure how relative URIs work if the request which calls virtual() was processed through Apache rewrite rules.

down

phpforum at joolee dot nl ¶

15 years ago

Problem with most of the scripts posted below is that virtual() flushes the pending headers before making the subrequest. Requesting an image with virtual() still returns a text/html type document.
A workaround is to set the content-type first. But that requires getting the content-type first.

I'm using the following script for now. A disadvantage is that Apache makes 2 subrequests.

<?PHP
$file = '/resources/7z.gif';
$file_info = apache_lookup_uri($file);
header('content-type: ' . $file_info -> content_type);
virtual($file);
die();
?>

down

david at audiogalaxy dot com ¶

25 years ago

Virtual returns the HTTP entity header after the requested file, when it's the first output to the page.



The work-around to prevent seeing the header is, of course, to output something (such as echo " "; ) before calling virtual.

down

php at n-wise dot com ¶

21 years ago

I saw the note above about the length of the query string... but didn't know what it was, so have altered the code so it can post to the script.
Probly only works on nix systems as it makes use of the echo function...
This code also will look evaluate the result, so you can get cgi to dynamically create PHP (probly best to watch out that posted variables do not include script!)
<?
$CGISCRIPT="./cgi-bin/cgiscript.cgi";
 // preparing the arguments passed to this PHP page 
$QSTRING = $QUERY_STRING; 

foreach ($HTTP_POST_VARS as $header=> $value ){
 if($QSTRING==""){
    $QSTRING = $header.'='.urlencode($value); 
 }else{
    $QSTRING = $QSTRING.'&'.$header.'='.urlencode($value); 
 }
}
 
putenv('REQUEST_METHOD=POST'); 
putenv('CONTENT_TYPE=application/x-www-form-urlencoded');
putenv('CONTENT_LENGTH='.strlen($QSTRING));
putenv('QUERY_STRING='.$QSTRING); 
unset($return_array); 
exec('echo "'.$QSTRING.'"| '.$CGISCRIPT, $return_array, $return_val); 

//The 1st line of my script was "Content...." ... so remove it!
$firstline=array_shift($return_array);
//evaluate the code
eval('?>'.implode($return_array,''));

?>

down

Anonymous at spam dot org ¶

17 years ago

Note that QUERY_STRING seems to get inherited, so to make a virtual request WITHOUT one, one needs to explicitly append a "?" to the URL of the sub-request (to cause the creation of a "null" query string).  Of course, if the desired URL has its own query string, that will override and an additional "?" should not be appended.

This was with PHP 4.4.7 (released May 2007).

down

ruibal_DELETED_p*AT*gmail__dot__com ¶

18 years ago

when php is installed as an apache module, this works pretty well for writing your own php preprocessor/information logger. For example, requests to any URI underneath pre.php will first be executed by pre.php, then returned to the user.
<?
$docroot        = $_SERVER['DOCUMENT_ROOT'];
$script_root    = str_replace( basename($_SERVER['SCRIPT_NAME']),'',$_SERVER['SCRIPT_NAME'] );
$script_ext     = substr( $_SERVER['SCRIPT_NAME'], strrpos( $_SERVER['SCRIPT_NAME'],'.' ) );
$fakework_root  = $script_root.basename( $_SERVER['SCRIPT_NAME'] ).'/';
$framework_root = $script_root.'_'.basename( $_SERVER['SCRIPT_NAME'], $script_ext ).'/';
$frequest_root  = dirname( $framework_root.substr( $_SERVER['PATH_INFO'], 1 )).'/';
$frequest_name  = basename( $_SERVER['PATH_INFO'] );
$frequest_ext   = (strrpos($frequest_name,'.')===FALSE ? FALSE : strtolower(substr( $frequest_name, ( strrpos( $frequest_name, '.' )+1 ) ) ) );
$frequest_full  = $frequest_root.$frequest_name;
$doc_frequest   = $docroot.$frequest_full;
$doc_framework   = $docroot.$framework_root;

$DO_PARSE = in_array( $frequest_ext, $chk_exts );
if( $DO_PARSE )
{
    $tmpfname = tempnam( $doc_framework.'tmp', 'aj_' ).($frequest_ext? ('.'.$frequest_ext) : '');
    if( ($to_parse=@file_get_contents($doc_frequest))===FALSE )
        $to_parse="404";
    $tmpvname = str_replace( $docroot, '', $tmpfname ); 
    $tmpvname = str_replace( '\\\\', '/', $tmpvname ); 
// - - - - - - - - - - - - - - - - - - - - - - - - - - -
//  Do processing of data stored in $to_parse
// - - - - - - - - - - - - - - - - - - - - - - - - - - -
    $to_parse = striptags( $to_parse );

// - - - - - - - - - - - - - - - - - - - - - - - - - - -
    $handle = fopen($tmpfname, "w");
    fwrite($handle, $to_parse);
    fclose($handle);
    @virtual( $tmpvname.$getvars );
    unlink( $tmpfname );
}
else
    @virtual( $frequest_full.$getvars );

?>

So all files in http://server/sub/pre.php/path/ are really located in http://server/sub/_pre/path/

All this needs is some kind of caching mechanism.

But yeah, this could be modified to add watermarks with the image functions, convert to xml with Tidy, check for extensions better with mimeTypes, proxy content with cURL, validate $_SERVER['HTTP_REFERER'] or $_SERVER['HTTP_USER_AGENT'], etc etc

This gives you much more over than the auto_prepend_file, and auto_append_file, for certain functionality

The key is the virtual function _because_ it delivers the modified content with an apache subrequest.

down

s dot dan at free dot fr ¶

23 years ago

Another way of passing arguments:

If you have some CGI programs that depend on some libraries where you can't change the source code (in my case an online payment library), you can pass the arguments by changing some environment variables.



Of course the CGI program has to get the GET/POST variables in the usual manner.

It simulates, more or less, a direct call from the server to a CGI program:



// preparing the arguments passed to this PHP page

$QSTRING = $QUERY_STRING;



// pay attention to the maximum length of the QUERY string.

while (list ($header, $value) = each ($HTTP_POST_VARS)){

  if (empty($QSTRING))

    $QSTRING = $header.'='.$value;

 else

    $QSTRING = $QSTRING.'&'.$header.'='.$value;

} 



putenv('REQUEST_METHOD=GET');

putenv('QUERY_STRING='.$QSTRING);



unset($return_array);

exec('my_CGI', $return_array, $return_val);



Now you can parse the output of 'my_CGI' in return_array.

down

logang at deltatee dot com ¶

23 years ago

If you want to pass all post and get values to the cgi script you can use this code:



<?php

$QSTRING = $QUERY_STRING;

while (list ($header, $value) = each ($HTTP_POST_VARS)) 

{

   $QSTRING = $QSTRING.'&'.$header.'='.$value;

}



virtual($script.'?'.$QSTRING);

?>



It takes all the values of $HTTP_POST_VARS and appends them in the proper format to the values you get in $QUERY_STRING

down

-1

jhibbard at gmail dot com ¶

15 years ago

While the virtual() function has it's promising sides, there exists issues when using it in relation to a cache system such as eAccellerator.  The issue becomes that the first time you load with a virtual file, it will seem to work fine.  But once the cache is put into play, the virtual call will end up returning nothing at all, and basically returning a blank page.

Please realize that this is not an issue with virtual(), but instead an issue of the cacheing application.  Should anyone else have a similar issue, hopefully this will shed some light onto this subject.

Jonathon Hibbard

down

-1

chardin at ssc dot wisc dot edu ¶

22 years ago

If you are having problems using virtual include becuase of files being stored in different directories, a root-relative path will make things much easier:

virtual ("/root directory/directory/filename.htm/");

where root directory is the root directory of your site (ask your sys admin if you dont know what it is) Don't include the protocol or host name.

This will also allow you to move your files around your site without having to redirect your includes which is *very* helpfull

down

-1

abentley at panoramicfeedback dot com ¶

21 years ago

Here's an update to tomwk's code:
function safe_virtual( $filename )
{
   $curDir = getcwd();
   virtual ( $filename );
   chdir( $curDir );
}

This is better if you've already changed your current directory to be something other than your script's directory.  It works for PHP4 and above.

＋add a note

virtual

Description

Parameters

Return Values

Examples

Notes

See Also

Found A Problem?

User Contributed Notes 14 notes