Confusion between bindValue() and bindParam()?

Question

I am confuse between these two functions Bindvalue() and BindParam()

1. I read on php.net it does not escape % and _, so be careful when using LIKE. So i think BindValue() is not used when we are using LIKE query.
2. when we using LIKE query BindParam() is used. Because as i know BindParam can escape these % and _.
3. BindValue() doesn't gives protection against sql injection. I am not sure about this, is it true?

friends tell what i mention in these 3 points is right or wrong. i am beginner in PDO so please explain it clearly ..

Answer 1

There should be no difference in how values are escaped or not escaped. bindParam differs from bindValue in that it references the variable, binding the value only when you execute the statement. bindValue takes the value immediately. To illustrate:

$stmt = $db->prepare('SELECT * FROM `table` WHERE foo = :foo');

$foo = 'foo';
$stmt->bindValue(':foo', $foo);
$foo = 'bar';

$stmt->execute();

The above executes like SELECT * FROM table WHERE foo = 'foo';

$stmt = $db->prepare('SELECT * FROM `table` WHERE foo = :foo');

$foo = 'foo';
$stmt->bindParam(':foo', $foo);
$foo = 'bar';

$stmt->execute()

The above executes like SELECT * FROM table WHERE foo = 'bar'.

It's true that neither cares about _ or % as special characters, because generally speaking they aren't special characters as far as the syntax is concerned, and the database driver is not able to analyze the context to figure out whether you mean % to be a wildcard or the actual character "%" in the context of a LIKE query.

Both protect against SQL injection.