PHP while循环回显重复

Question

I need some help with some methodology

I have a SQL statement that fetches results from a questions 'header table'.

while() the data is being fetched I'm running another SQL statement that pulls comments from a 'sub table' according to the id fetched from the questions table.

When I echo all together, question number 1's comments show fine, all the comments related to the question are showing fine.

The issue is when question number 2's comments are echoed, comments from question number 1 show up (duplicated).

I just can't figure out where I'm going wrong.

Here's a simplified version of what my code looks like just to show the methodology:

$comment_list = ""; // to display comments
$GET_QUESTIONS = $DBH->prepare("SELECT ...");
// parameters are bound here using $GET_STATEMENTS->bindParam();

while($row = $GET_QUESTIONS->fetch(PDO::FETCH_ASSOC)){

    $question_id = $row['id'];
    $question_string = $row['string'];

    // NOW I PULL THE COMMENTS
    $GET_COMMENTS = $DBH->prepare("SELECT ...");
    // parameters are bound here using $GET_COMMENTS->bindParam();

    while($row = $GET_COMMENTS->fetch(PDO::FETCH_ASSOC)){

        $comment_id = $row['id'];
        $comment_string = $row['string'];

        $comment_list .= "
            <p>" .$comment_string. "</p>
        ";

    }

    echo "
        <h1>" .$question_string. "</h1>
        " .$comment_list. "

    ";

}

Why are the duplicates happening when echoing the second question?

Answer 1

You've to reset the $comment_list variable before the second while loop. Set it as

$comment_list = null ; 

Just before the second while loop. That's all !