Yes, the crontab entry is merely to make sure your local PHP install stays up-to-date.
Did you make the required changes to your .htaccess file? The local install will not be used if you do not do this. The following lines need to be added to your .htaccess file (or the file created if you don't already have one).
AddHandler php-cgi .php
Action php-cgi /cgi-bin/php.cgi
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