Is it bad practice to query a database without providing a link identifier?

In PHP, it is possible to do things like $results = mysql_query("select ....");

(see how no link identifier was provided).

The only thing that requires is that a mysql_connect() function has been called before, successfully.

Now I 开发者_JS百科tend to alway provide a link identifier but I don't really know why.

Is calling queries without a link identifier any less secure than the other way (providing the link identifier in every query)?

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The link identifier is needed when you have an application that needs to connect to more than one database server in the same request/transaction.

It's a good idea to use it even if you only have one database. "Explicit is better." Oh wait, that's Python.

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No, it is not any less safe.

However, using mysql_*() functions are less safe than PDO because they don't have parameter binding by default.

If you switcht to PDO and use bindParam(), then it is safer than mysql_*().

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If the system will never connect to multiple databases, there are no consequences in practice. I'm sure there are some in theory, which I will be informed of via flaming comments in no time!