PHP: Sort divs by class

If you can't do it with javascript ... order before rendering the page. Example with a kind of MVC:

1. Masterdata
2. Rendering

So:

<?php
// $data is filled BDD or any source
$output = [];
foreach( $data as $row ) {
  $content = '<div class="' . $row['my-class'] . '">...</div>';
  $output[] = ['key' => $row['my-class'], 'content' => $content];
}

usort($output, function($a, $b) {
  return $a['key'] < $b['key'];
});

foreach( $output as $row ) {
  echo $row['content'];
}

I used a 2D array. Of course, you could use another ways as:

$output = [];
foreach( $data as $row ) {
  $key = $row['my-class'] . '-' . count($output);
  $output[$key] = $content;
}

ksort($output);

foreach( $output as $row ) {
  echo $row;
}

If for some reason you can´t use the variable that gives the name to your class, I would use a regex to accomplish this

$html='
    <div class="1">...</div>
    <div class="2">...</div>
    <div class="1">...</div>
    <div class="3">...</div>
    <div class="2">...</div>
';
$regex="/<div.*class=\"(.*?)\">.*?<\/div>/";
$numItems = preg_match_all($regex, $html, $matches);

$arr = array();

for ( $i = 0; $i < $numItems; $i++ ){
    $arr[$i] = array();
    $arr[$i]["code"] = $matches[0][$i];
    $arr[$i]["className"] = $matches[1][$i];
}

usort($arr, function($a, $b){ return strcmp($a["className"], $b["className"]); });
$arr = array_map(function($a){ return $a["code"]; }, $arr);
$sortedHtml = implode($arr);