Description:
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Null handling in atleast PDO sqlite driver seems broken.

Seems impossible to use prepared statements with NULL values. They appear to get converted to an empty string.

Reproduce code:
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<?php
	$pdo = new PDO('sqlite::memory:');
	$pdo->exec('CREATE TABLE test(ID INT NOT NULL PRIMARY KEY, Field VARCHAR(12) NULL);');
	$stmt = $pdo->prepare('INSERT INTO test(ID, Field) VALUES(?, ?)');

	$one = 1;
	$two = 2;
	$null = NULL;
// Try with PDO_PARAM_NULL
	$stmt->bindParam(1, $one, PDO_PARAM_INT);
	$stmt->bindParam(2, $null, PDO_PARAM_NULL);
	assert($stmt->execute());
// Try with PDO_PARAM_STR
	$stmt->bindParam(1, $two, PDO_PARAM_INT);
	$stmt->bindParam(2, $null, PDO_PARAM_STR);
	assert($stmt->execute());
// Check we have rows..
	$stmt = $pdo->prepare('SELECT * FROM test');
	assert($stmt->execute());
	var_dump($stmt->fetchAll(PDO_FETCH_OBJ));
// Check we have rows with field is null
	echo '<hr />';
	$stmt = $pdo->prepare('SELECT * FROM test WHERE Field IS NULL');
	assert($stmt->execute());
	var_dump($stmt->fetchAll(PDO_FETCH_OBJ));
?>

Expected result:
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2 rows in table test where Field column is null.

Actual result:
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2 Rows in table test with Field is an empty string.