As previously reported in bug report # 1971..  

I am running the 4.0.0 release of PHP and can not access global variables outside of the function
when the arrays had been reset with unset().

Here's the function :

function get_images($lognum)  {
global $small_images, $large_images, $num_images;

$ls_command = "ls pics/logs/" . $lognum . "s*.jpg";
$image_name = "pics/logs/" . $lognum . "s.jpg";

if (file_exists($image_name))  {
  unset($small_images);
  exec($ls_command,$small_images);
  $ls_command = "ls pics/logs/" . $lognum . "l*.jpg";
  unset($large_images);
  exec($ls_command,$large_images);
  $num_images = count($small_images);
  }
else
  $num_images = -1;
}

Then when I do:
get_images($row["lognum"]);
print $small_images[0];

I get no values returned.  When I comment the unset lines everything works perfectly.

When I run a phpinfo(), here is some of the information that's provided:
FreeBSD my.systemname.com 4.0-RELEASE FreeBSD 4.0-RELEASE #0: Mon Mar
                                                     20 22:50:22 GMT 2000
                                      root@monster.cdrom.com:/usr/src/sys/compile/GENERIC i386

'./configure' '--prefix=/usr/local' 'i386--freebsd4.0' '--with-system-regex'
                                     '--with-apache=/usr/ports/www/apache13-php4/work/apache_1.3.12'
                                   '--with-config-file-path=/usr/local/etc' '--disable-debug' '--enable-track-vars'
                                      '--without-gd' '--disable-pear' '--with-zlib' '--with-mcrypt=/usr/local'
                                                 '--with-xml=/usr/local' '--enable-ftp'