Is there a limit on the length of command passed to exec in PHP?

Question

Currently I need to merge that 50+ PDF files into 1 PDF. I am using PDFTK. Using the guide from: http://www.johnboy.com/blog/merge-multiple-pdf-files-with-php

But it is not working. I have verified the following:

1. I have tried the command to merge 2 pdfs from my PHP and it is working.
2. I have echo the final command and copied that command and paste into command prompt and run manually and all the 50 PDFs are successfully merged.

Thus exec in my PHP and the command to merge 50 PDFs are both correct but it is not working when done together in PHP. I have also stated set_time_limit(0) to prevent any timeout but still not working.

Any idea what's wrong?

Answer 1

You can try to find out yourself:

print exec(str_repeat(' ', 5000) . 'whoami');

I think it's 8192, at least on my system, because it fails with strings larger than 10K, but it still works with strings shorter than 7K