Class 'Craft\DbCommand' not found Getting this error in the PHP error log file while trying to install craft. 

PHP Fatal error:  Class 'Craft\DbCommand' not found

The file is there, permissions are granted and I've tried reinstalling twice. Any other ideas?
Even thought this is an old thread, I recently ran in to the same problem. It turned out to be a PHP version issue. I was running MAMP with PHP 7.0.0, once I switched that host to 5.6.10 it worked perfectly.