passthru loses php posted variables

Anyone come across something like this before? I have made a little test script as follows: <? header ("Content-Type: application/pdf"); $command_line = "/usr/bin/pdflabelseries " . escapeshellcmd($_POST['labelstart']) . " " . escapeshellcmd($_POST['labelend']); exec ("echo \"$command_line\" >/opt/specs/labels.txt"); //passthru($command_line); ?> The form takes input from a posted form with two variables, labelstart and labelend. In the above test, if I put in 'start' and 'end' as the posted variable data, the output from /opt/specs/labels.txt (writable by the http server) is: /usr/bin/pdflabelseries start end All is well and good. Now is where it heads South. I uncomment the passthru command above. The output from the script in /opt/specs/labels.txt from the same posted form with the same data entered is now: /usr/bin/pdflabelseries pdflabelseries is a C program that I have confirmed works perfectly on the command line (i.e. generates the requisite pdf file to stdout). Even if the C program fails (which it does not appear to do from the output in the httpd logs as it outputs its command line to stderr), surely php should not lose its own internal variables, especially, for a command that is executed BEFORE the passthru command. I am truly baffled. Any help appreciated. Regards Mark I am running vanilla Mandrake 9.1 with the following PHP rpms: libphp_common430-430-11mdk php-pear-4.3.0-3mdk apache2-mod_php-2.0.44_4.3.1-2mdk php-xml-4.3.0-2mdk php-dba_bundle-4.3.0-4mdk php-pgsql-4.3.0-4mdk php-xmlrpc-4.3.0-2mdk php-manual-en-4.3.0-2mdk php430-devel-430-11mdk php-gd-4.3.0-2mdk