title: What do the flags in crontabs mean?
body: <p>I have this line in my crontab:</p>
  
  <pre><code>0 0 * * * /usr/local/bin/php5 -d allow_url_fopen=on -f /path/to/file.php
  </code></pre>
  
  <p>I cannot find any comprehensive reference on the meaning of the "-d" and "-f" flags. What do they mean? And is there a page that explains these and other flags?</p>