如何在stmt中绑定绑定结果中的参数

Question

I want to bind the result from prepared query which is in while stmt. But it gives me the error

Call to a member function bind_param

We all know this obvious error message... I just don't know why is this error popping out...

Here is my php code (session is started and all rows and columns are correct)

$selectposts = "SELECT postby,posttxt,time,upvotes,downvotes FROM posts ORDER BY id DESC";
$stmt = $mysqli->prepare($selectposts);
$stmt->execute();
$stmt->bind_result($postby,$posttxt,$posttime,$upvotes,$downvotes);
while($stmt->fetch()){
   $picturestmt = $mysqli->prepare("SELECT picture FROM members WHERE username = ?");
        $picturestmt->bind_param('s', $postby);
        $picturestmt->execute();
        $picturestmt->bind_result($picture);
                        while($picturestmt->fetch()){
                                if(empty($picture)){
                                        $profpicturefromdb = " <img src='profile_pictures/public_icon.png' width='25' height='25' class='fxdmimg'>";
                                } else {
                                        $profpicturefromdb = " <img width='25' class='fxdmimg' height='25' src='profile_pictures/".$picture."' alt='Profile Picture'>";
                                }
                        }
}

This code should assign the $profpicturefromdb to an image. (And also pull out all posts from database but that's another echo)

If I echo the $postby, it shows the name of user who posted the post. That's fine, but why it does not assign that to the "bind_param('s',$postby'); ? Thanks

Answer 1

The full error is:

Call to a member function bind_param on a non-object

This means $picturestmt isn't an object when you call:

$picturestmt->bind_param('s', $postby);

As you could see from var_dump($picturestmt): $picturestmt is false.

So we can see, technically, false->bind_param is generating that error.

You have to turn to debugging why mysqli_prepare is returning false:

$picturestmt = $mysqli->prepare("SELECT picture FROM members WHERE username = ?");

This can be done using mysqli::error