bind_param() doesn't seem to work

Question

I have the following code:

Answer 1

mysqli_stmt_bind_param accepts variables (by reference). You cannot use literals. Change your code to

$fileSize = 123;
$stmt->bind_param('ssi', $string1, $string2, $fileSize);

Answer 2

Please try the variable assignment after bind_param(). It is a passed by reference call. So it will work after also.

$stmt = $db->prepare("INSERT INTO images (filename, mime_type, file_size) VALUES (?, ?, ?)");
$stmt->bind_param('ssi', $string1, $string2, $num);
$string1 = 'string 1';
$string2 = 'string 2';
$num=123;
$stmt->execute();