I'm not sure what value you need to give "log", so you should replace it with the appropriate value in your cron job. Check the following article to see more of a reference for passing the variables in a PHP script.
I hope this helps to clarify the issue! If you have any further questions, please let us know.
I took a long through PHP documentation, asked a few systems people here, and then took another look through forums. I can find NO example of log used as a parameter, especially in the way you're using it. However, it doesn't mean that it isn't correct. First, are you getting any PHP errors that are logged when you try to use the log parameter in the cron job? Also, what exactly are you trying to do with the parameter? There are other commands (which have values assigned for their function) that may do what you want. Check out this article and see if it matches up with up you're trying to accomplish: PHP Error and Logging. Otherwise, you may need to consult with a programmer for this particular answer. If you can give us a little more information, we might be able to find the answer for you.
Hope that helps to point you in the right direction. Please let us know if you require any further assistance.