Trying to use mysql query inside of a php function to call data from database.

Question

I've created a function called tree() which is supposed to retrieve data from my comments table and display comments in a thread in a hierarchy, much like the comments on reddit. The $parentid is the id of the parent comment and the $postid is the id of the page the comment is on. DisplayComments() is a php function which displays the comment's data and forms, including html.

Now the issue is when I load the page the php code stops at $statement = $databaseConnection->prepare($query); when it's done inside of the function. However, if I take the code outside of the function the code works, but I can't use the code inside of DisplayComments() and can only show the comment replies as if they were the start of new threads.

Why can't I use this mysql query inside of a function? Is there anyway I can use it inside of a function so I can call it where I need it?

function tree($parentid, $postid) {
    $query = "SELECT * FROM comments WHERE parentid = ?";
    $statement = $databaseConnection->prepare($query);
    $statement->bind_param('i', $parentid);
    $statement->execute();
    $statement->store_result();
    if ($statement->error)
    {
        die('Database query failed: ' . $statement->error);
    }

    if ($statement->num_rows >= 1)
    {
        $statement->bind_result($commentid, $postid, $username, $comment, $parentid, $level);
        while($statement->fetch()){
            if (!is_hidden($commentid, 1)){ 
                DisplayComments($comment, $username, $postid, $commentid, $level);
            }   
        }
    }
}

If you want to learn how to write a good code, learn about Data Mapper / Repository pattern. — Yang
– Yang, Commented Mar 7, 2015 at 14:54

rjdown · Accepted Answer · 2015-03-07 14:52:16Z

1

Your tree function has no knowledge of $databaseConnection. You need to pass it as another variable, e.g.

function tree($parentid, $postid, $databaseConnection) {

Have a read of the PHP manual's page on variable scope (but try not to use global, that's rarely a good thing)

answered Mar 7, 2015 at 14:52

rjdown

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5 Comments

The_Perfect_Username Over a year ago

It partially works. It displays one nested comment but now that comment has the previous issue. I should mention that DisplayComment() calls tree() inside of itself too so they loop around another.

rjdown Over a year ago

This line $statement->bind_result($commentid, $postid, $username, $comment, $parentid, $level); contains more variables that are out of scope. You're going to need to pass those too

The_Perfect_Username Over a year ago

The bind-result is me passing the selected data from the database into variables. How are these out of scope?

The_Perfect_Username Over a year ago

No problem. Is there anything else you can see which I could fix?

The_Perfect_Username Over a year ago

Nevermind. I fixed it! Instead of doing function tree($parentid, $postid, $databaseConnection) I just created a global variable and placed it in the function. Thanks for your help though!

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