Permission denied for www-data accessing /dev/video0 w/php

[mytomi]

I'm running Raspbian 3.6.11+ #538. I have a php web page on lighttpd to take webcam photos with fswebcam.

The php part:

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<?php
$command = "/var/www/bin/TakeAnotherPic.sh";
echo "<H1>Taking a picture at the moment...</H1>\n";
$output = shell_exec($command);
echo "$output";
?>

The script:

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#!/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
whoami #debug
/usr/bin/fswebcam -v -r 640x480 /var/www/webcam/$(date +\%Y-\%m-\%d-\%H-\%M).jpg 2> /var/www/bin/fswebcam.txt

Now, when running from command line, as user www-data (su www-data), everything works just right. The webcam pic is saved in the right directory.

When running the script from php web page (confirmed user is www-data), the script excecutes, but the fswebcam part fails with error messages:

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--- Opening /dev/video0...
Trying source module v4l2...
Error opening device: /dev/video0
open: Permission denied
Trying source module v4l1...
Error opening device: /dev/video0
open: Permission denied
Unable to find a source module that can read /dev/video0.

Further info

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# ls -la /dev/video0
crw-rw---T 1 root video 81, 0 Nov  6 10:35 /dev/video0

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# grep video /etc/group
video:x:44:pi,www-data

The webcam is Microsoft Lifecam 5000 connected via externally powered USB hub.

How come the permissions for www-data are different when executing the script from php or from command line? What am I missing here? I suspect an easy fix, but what on earth is it?

Thanks

[DougieLawson]

Are you sure that PHP is running as www-data?

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<?php
echo "<p>Current User ID is: ". posix_getuid();
echo "<p>Current Group ID is: ". posix_getgid();
?>

Are you sure when it runs the script with shell_exec() that the spawned process is running with www-data?
Are you running FastCGI? Is that chrooted (for security reasons)?

[mytomi]

Problem solved. I had to uncomment a line in php.ini:

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cgi.fix_pathinfo = 1

Thanks for leading me to the right direction!