Wrapping foreach result in a div - php

Question

I have this function working great
<?php
$categories = get_categories(array(
'hide_empty' => 0,
'taxonomy' => 'category',
'orderby' => 'title',
'order' => 'ASC'
));
foreach ($categories as $category) {
$firstletter = strtoupper(substr($category->name,0,1));
$link = get_category_link( $category->term_id );
if ($firstletter != $current) {
$postlist .= "<b><a name='$firstletter'> $firstletter </a></b><br>\n";
$nav .= "<a href='#$firstletter'> $firstletter </a> ";
$current = $firstletter;
}
$postlist .= "<a href='$link'>" . $category->cat_name . "</a><br>\n";
}
print $nav . "<br>" . $postlist;
?>
What I need, is to wrap the entire list starting with the letter. For example, Letter M will be wrapped in a div with all the categories starting with M.
This is what I currently get: http://i.imgur.com/PEmJw03.png - Any help would be appreciated, thank you.

Answer 1

You seem to be on the right path. I think this is what you are requesting to do:
$closeLastDiv = false;
foreach ($categories as $category) {
$firstletter = strtoupper(substr($category->name,0,1));
$link = get_category_link( $category->term_id );
if ($firstletter != $current) {
if ($firstletter == ""){ //first time through
$postlist .= "<div>";
$closeLastDiv = true;
} else {
$postlist .= "</div><div>";
}
$postlist .= "<b><a name='$firstletter'> $firstletter </a></b><br>\n";
$nav .= "<a href='#$firstletter'> $firstletter </a> ";
$current = $firstletter;
}
$postlist .= "<a href='$link'>" . $category->cat_name . "</a><br>\n";
}
if ($closeLastDiv) {
$postlist .= "</div>";
}

Answer 2

All you need is comparte the current letter with before letter, and if changed print the starting wrapper + content. When the letter changes, close the wrapper and open the next wraper.
Something like this:
$current = "-";
$postlist .= "<div>";
foreach ($categories as $category) {
$firstletter = strtoupper(substr($category->name,0,1));
$link = get_category_link( $category->term_id );
if ($firstletter != $current) {
$postlist .= "</div><div id='{$firstletter}'>";
$postlist .= "<b><a name='{$firstletter}'>".$firstletter."</a></b><br>\n";
$nav .= "<a href='#{$firstletter}'>".$firstletter."</a> ";
$current = $firstletter;
}
$postlist .= "<a href='$link'>" . $category->cat_name . "</a><br>";
}
$postlist .= "</div>";
The first div remain empty, but all other are ok.