problems running php script via cron

I'm trying to execute a php script via cron. The script works fine run through the browser. The file is chmod 755. The cron file is

# m h  dom mon dow   command
* * * * * /opt/bitnami/apache2/htdocs/myscript.php

I have verified cron is running using

bitnami@ip-12-345-789-012:/usr/local/bin$ ps aux | grep cron
root       496  0.0  0.1   2400   916 ?        Ss   Nov03   0:00 cron

EDIT: I have fixed by changing crontab file to

m h  dom mon dow   command
* * * * * /opt/bitnami/php/bin/php /opt/bitnami/apache2/htdocs/myscript.php

I am curious what the difference is supplying the path to php this way or via a shebang in the script? are they equivalent or do I misunderstand?