Originally Posted by sundialsvcs

Exactly so. "The SQL statement that is to be executed" is found only in supplied string, which does not have any user-provided content. This statement, in the example above, has four input-parameters which must be supplied with values each time the prepared statement-handle ($stmt ...) is executed. Different parameter values may be provided each time $stmt is executed: there is no need to re-prepare the handle. Even if the parameter values "look like SQL," they are interpreted only as character-strings (or whatever data-type you said they were ...). In other words, they are input data to the query; never a part of the query itself.

This is not only more secure, but also more efficient. The SQL engine parses the SQL and prepares the "execution plan," as represented by the statement-handle, only one time. And, if you happen to be executing a statement millions of times, that does make a measurable difference.

It utterly baffles me why PHP did not provide easy access to this facility from the very start. (And why, when they finally did add it, they did not make it "easy.") It has always been available.