let references to PDO equal a PDO object and not PDO itself--
I see here that there is both PDO->query() and PDO->exec(). In the page that was linked, it appears that PDO->query(); is used for SELECT statements ONLY, and PDO->exec() is used for UPDATE,INSERT,DELETE statements. Now, I am brand new to PDO, so I'm not sure what is going on in terms of using it quite yet, so I would appreciate an explanation on why to use the different methods, and why there are different methods.
Despite of whatever theoretical difference, none of these functions should be used anyway - so, there is nothing to concern of.
The only reason of using PDO is support for prepared statements, but none of these functions offers it. So, they shouldn't be used.
Use prepare()/execute() instead, especially for UPDATE,INSERT,DELETE statements.
Please note that although prepared statements are widely advertised as a security measure, it is only to attract people's attention. But their real purpose is proper query formatting. Which gives you security too - as properly formatted query cannot be injected as well - just as side effect. But again - formatting is a primary goal, just because even innocent data may cause a query error if not formatted properly.
EDIT:
Please note that execute() returns only TRUE or FALSE to indicate success of the operation. For other information, such as the number of records affected by an UPDATE, methods such as rowCount() are provided. See the docs.
