I'm developing a web site in PHP for an Apache server.

I have a particular stand-alone application that takes a text file as
input, and produces a text-file as output. It's usually run from the
Unix command line. I'd like my PHP code to provide the input text file,
run the stand-alone application, and then read the output text file and
reformat it for display on the site.

Is there a way for my PHP app, to cause this Unix command-line
application to run?

Thanks in advance to all for any info.