Linux – How to kill a runaway cronjob

I have a cronjob that is set to run constantly. It's a php file that streams data from twitter. However twitter goes down every once a while or we lose connection so I have cron checking back every minute to try and run the file. The php script checks a lock file to make sure multiple copies are not run. The thing is this script will run for hours on end and I want to be able to kill it. However I can't seem to find it using commands like

ps ux

The cronjob was started with my user and I have looked to see it under root. I cannot seem to find the process running at all.

I am using

/usr/bin/php /var/www/twitter/stream.php

to execute in my cron file and I know it is running because every minute it writes a file to a directory. I can stop cron, but the process keeps going, I simply need to kill it. Not sure if this belongs here or on Stack Overflow.