Had the same issue and just figured, website is running under MAMP's php, but when you call in command, it runs mac's(if no bash path modified). you will have issue when mac doesn't have those extensions.
run php -i to find out loaded extensions, and install those one you missed. or run '/Applications/MAMP/bin/php/php5.3.6/bin/php artisan {your command}' to use MAMP's