php exec() Linux server strange output - php

Question

I am attempting to backround a php script since it will take more than a minute to complete and I do not want the user to wait.
my exec command is as follows:
exec ('php -f path/to/file.php > path/to/output.log 2>&1 &');
first of all the script in the file didnt do what i programmed it to do however, the output file still recieves this output:
X-Powered-By: PHP/5.6.24
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Pragma: no-cache
Content-Type: text/html; charset=UTF-8
Link: <https://example.com/wp-json/>;
rel="https://api.w.org/"
Link: <https://example.com/?p=687>; rel=shortlink
....
This output is not at all what my script is supposed to make, it makes no sense to me.
the rest of the output is a html document with differnet links to my website and such.
can anyone clue me into why this is happening and not simply running the script?
BTW
I have used different commands like /usr/bin/php with the same affect
UPDATE
I noticed that after changing the first path/to/file.php paremeter to gibberish i.e.
exec ('php -f asdfjaskldfj > path/to/output.log 2>&1 &');
that the output remains the same, not sure what this means but i believe it to be noteworthy

Answer 1

After must trial and error I found that
usr/bin/php
pointed to a php command that only outputted documentation on my current server, and when I changed it to
usr/bin/php5
it worked. Very hard to find documentation on the linux php command, and I still have yet to find anyone else with the same problem, but it has been resolved nonetheless.