Hi,
on my server, the pdf conversion with libreoffice didn't work.
After inspection, the command
passthru($libreOfficePath . ' --invisible --convert-to ' . $extension . ' ' . $docSource . ' --outdir ' . $outdir . $outputDebug, $codeReturn);
returned an int(77) inside $codeReturn (ie. a "permission denied" unix code)
The command
passthru('whoami');
correctly displays 'apache'
Finally, I understood that on my server the user 'apache' has no home directory.
My solution to make the convertor work correctly was to add the shell variable before :
passthru('export HOME=/tmp; ' . $libreOfficePath . ' --invisible --convert-to ' . $extension . ' ' . $docSource . ' --outdir ' . $outdir . $outputDebug);
Hope that this solution will help.