separate html from php comments class

Question

I found this class for threaded comment using php and MySQL:

<?php
class Threaded_comments
{

public $parents  = array();
public $children = array();

/**
 * @param array $comments
 */ 
function __construct($comments)
{
    foreach ($comments as $comment)
    {
        if ($comment['parent_id'] === NULL)
        {
            $this->parents[$comment['id']][] = $comment;
        }
        else
        {
            $this->children[$comment['parent_id']][] = $comment;
        }
    }
}

/**
 * @param array $comment
 * @param int $depth
 */ 
private function format_comment($comment, $depth)
{
    for ($depth; $depth > 0; $depth--)
    {
        echo "\t";
    }

    echo $comment['text'];
    echo "\n";
}

/**
 * @param array $comment
 * @param int $depth
 */ 
private function print_parent($comment, $depth = 0)
{
    foreach ($comment as $c)
    {
        $this->format_comment($c, $depth);

        if (isset($this->children[$c['id']]))
        {
            $this->print_parent($this->children[$c['id']], $depth + 1);
        }
    }
}

public function print_comments()
{
    foreach ($this->parents as $c)
    {
        $this->print_parent($c);
    }
}

}

this worked with this array:

$comment = array(  array('id'=>1, 'parent_id'=>NULL,   'text'=>'Parent'),  
                    array('id'=>2, 'parent_id'=>1,      'text'=>'Child'),  
                    array('id'=>3, 'parent_id'=>2,      'text'=>'Child Third level'),  
                    array('id'=>4, 'parent_id'=>NULL,   'text'=>'Second Parent'),  
                    array('id'=>5, 'parent_id'=>4,   'text'=>'Second Child')  
                );  

and for result:

$tc = new Threaded_comments($comment);
$tc->print_comments();

and result is:

Parent
    Child
        Child Third level
Second Parent
    Second Child

this worked true But for defign comment list(html) I need to add all html code into private function format_comment($comment, $depth). this is not good way and I think need separate html from php class.

EDIT:(this is my page for show/print threaded comment)

function _comments_($id,$type){
    $DB_QUERY = mySqli::f("SELECT id,user,email,message,timestamp,parent_id,rfield_1,rfield_2,rfield_3,rfield_4,rfield_5 FROM " . NEWS_COMMENTS . " LEFT JOIN " . NEWS_REVIEWS . " ON " . NEWS_COMMENTS . ".id = " . NEWS_REVIEWS . ".cid WHERE 
    pid = ? AND type = ? AND approved = 1 ORDER BY timestamp DESC LIMIT 12", $id, $type);

        foreach($DB_QUERY as $row){
         $commentdata[] = $row;
        }
    return $commentdata;
}
$comments_list = _comments_('125','book');
foreach($comments_list as $row){
        $comments[] = array(
        'id' => $row['id'],
        'parent_id' => $row['parent_id'],
        'name' => $row['user'],
        'text' => $row['message'],
        'datetime' => $row['timestamp']
        );
        }

        $tc = new Threaded_comments($comments);
        $tc->print_comments();

In my page threaded comments show with format_comment and work true. in case i need to design output using separate html from php class.

how do we separate html code from class in this case?!

Answer 1

You're right.

1) Most simple solution is to pass your array to a template. This template doesn't contain logic, but only html and php (e.g. foreach of your your array).

2) For beter separation, use Model-View-Controller pattern:

With this layer construction, each layer has its own responsibilities. Never html in model and controller. Queries in the models only.

Frameworks as Laravel and CodeIgniter have an implementation of this pattern.