If you ever try to format date in PHP and MySQL, using date (datetime or timestamp) value directly from MySQL to PHP date() function, then you'll get a Notice level error, something like this:
Notice: A non well formed numeric value encountered in ... .. .
Additionally, PHP date() will always return January, 01 1970 if MySQL date is directly used. It means, there is a difference between date in PHP and date in MySQL (i.e. they are not compatible). PHP date function accepts Unix Timestamp, which is different from MySQL date types (DATE, TIME, DATETIME, TIMESTAMP etc.)