Template system while in a while - php

Question

I am trying to make put comments below the answers that I loop (just like answers on stackoverflow) But I can't find out how to put the right comment below the right answer. I am using the template system with this.
With what I currently have it only shows the comments of the query with the last $row['id']
PHP Code:
<?php
//Query setup for answers
$answerquery = "SELECT a.id, a.post_id, a.username, a.date, a.text FROM answers_tbl AS a, posts_tbl AS p WHERE a.post_id = p.id";
$result = $mysqli->query($answerquery);
//Replace answers
$layout_a = file_get_contents("tpl/question_answer_layout.html");
$search_a = array("%username%", "%date_a%", "%text_a%");
$answer_r = NULL;
while($row = $result->fetch_array()){
$replace_a = array($row['username'], $row['date'], $row['text']);
$answer_r .= str_replace($search_a, $replace_a, $layout_a);
//Query setup for comments of the question
$commentquery = "SELECT c.username, c.comment
FROM answer_comments_tbl AS c
INNER JOIN answers_tbl AS a ON a.id = c.answer_id
WHERE answer_id =".$row['id'];
$result2 = $mysqli->query($commentquery);
//Replace comments
$layout_c = file_get_contents("tpl/question_comment_layout.html");
$search_c = array("%comment_c%", "%username_c%");
$answer_c = NULL;
while($row2 = $result2->fetch_assoc()){
$replace_c = array($row2['comment'], $row2['username']);
$answer_c = str_replace($search_c, $replace_c, $layout_c);
$answer_r = str_replace("%answer_comment%", $answer_c, $answer_r);
}
}
$template = str_replace("%answer_post%", $answer_r, $template);
?>
question_answer_layout.html:
<div id="AnswerCarTop">
</div><!--Question-->
<div id="QuestionBottom">
<div id="QuestionTitle">%username%</div><!--QuestionTitle-->
<div id="Paragraph">%text_a%</div><!--Paragraph-->
%answer_comment%
question_comment_layout.html:
<div id="CommentPlaced">
<div id="Paragraph1">%comment% - <span class="bold">%username%</span></div>
<!--Paragraph--></div>

Answer 1

There are a few problems with your code that prevent it from working correctly.
First of all, the query to retrieve the comments needs to do a join between the two tables you are using, otherwise it will perform a cartesian product of the two tables (every answer is joined to every comment and then filtered by where). You should rewrite it as:
SELECT c.username, c.comment
FROM answer_comments_tbl AS c
INNER JOIN answers_tbl AS a ON a.id = c.answer_id
WHERE answer_id = $row['id']
Of course, using prepared statements is another matter entirely.
The second problem is the order in which you're doing your replacements. The basic structure (in pseudocode) should be:
for each answer {
for each comment {
comment = apply the comment template
comments_string += comment
}
apply the posts template, using the previously calculated comments_string
}
The third problem is the general approach of performing a separate query for every answer. You can solve this problem with just 2 queries (or even a single one, but then it's a more delicate matter which will certainly derive into its own discussion). The better approach would be to get all the answers for the post, then get all the comments that are related to that post. After that you can group up the comments to know where each one comes from.
Here is the fully edited code. I didn't add prepared statements because it's beyond the scope of this answer, but you should definitely use them.
<?php
//Query setup for answers
$answerquery = "
SELECT a.id, a.post_id, a.username, a.date, a.text
FROM answers_tbl AS a
INNER JOIN posts_tbl AS p ON a.post_id = p.id
WHERE p.id = " . (int) $post_id;
$answerResult = $mysqli->query( $answerquery );
// Query setup for comments
$commentsQuery = "
SELECT c.username, c.comment, c.answer_id
FROM answer_comments_tbl AS c
INNER JOIN answers_tbl AS a ON a.id = c.answer_id
WHERE a.post_id = " . (int) $post_id;
$commentsResult = $mysqli->query( $commentsQuery );
// Group the comments by answer
$groupedComments = array();
while( $row = $mysqli->fetch_assoc( $commentsResult ) ) {
if( ! isset( $groupedComments[ $row['answer_id'] ] ) ) {
$groupedComments[ $row['answer_id'] ] = array();
}
$groupedComments[ $row['answer_id'] ][] = $row;
}
// Loading the template files only once
$layout_a = file_get_contents( 'tpl/question_answer_layout.html' );
$search_a = array( '%username%', '%date_a%', '%text_a%');
$layout_c = file_get_contents( 'tpl/question_comment_layout.html' );
$search_c = array( '%comment%', '%username%');
// This will hold the string with all the answers and their comments
$answers = null;
while( $row = $answerResult->fetch_assoc() ) {
// This will hold all the comments for the current answer
$answer_comment = null;
foreach( $groupedComments[ $row['id'] ] as $comment ) {
// Apply the comment layout
$replace_c = array( $comment['comment'], $comment['username'] );
$answer_comment .= str_replace( $search_c, $replace_c, $layout_c );
}
// Apply the answer layout
$replace_a = array( $row['username'], $row['date'], $row['text'], $answer_comment );
$answers .= str_replace( $search_a, $replace_a, $layout_a );
}
// Add all the answers and the comments to the main template
$template = str_replace( '%answer_post%', $answers, $template );

Answer 2

This worked for me and solved my question:
<?php
//Query setup for answers
$answerquery = "SELECT a.id, a.post_id, a.username, a.date, a.text FROM answers_tbl AS a, posts_tbl AS p WHERE a.post_id = p.id";
$result = $mysqli->query($answerquery);
//Replace answers
$layout_a = file_get_contents("tpl/question_answer_layout.html");
$search_a = array("%username%", "%date_a%", "%text_a%");
$answer_r = NULL;
while($row = $result->fetch_array()){
$replace_a = array($row['username'], $row['date'], $row['text']);
$answer_r .= str_replace($search_a, $replace_a, $layout_a);
//Query setup for comments of the question
$commentquery = "SELECT c.username, c.comment
FROM answer_comments_tbl AS c
INNER JOIN answers_tbl AS a ON a.id = c.answer_id
WHERE answer_id =".$row['id'];
$result2 = $mysqli->query($commentquery);
//Replace comments
$layout_c = file_get_contents("tpl/question_comment_layout.html");
$search_c = array("%comment%", "%username%");
$answer_c = NULL;
while($row2 = $result2->fetch_assoc()){
$replace_c = array($row2['comment'], $row2['username']);
$answer_c .= str_replace($search_c, $replace_c, $layout_c);
}
$answer_r = str_replace("%answer_comment%", $answer_c, $answer_r);
}
$template = str_replace("%answer_post%", $answer_r, $template);
?>