02. Semantic HTML

<?php

$semantic = ['main', 'header', 'nav', 'article', 'section', 'aside', 'footer'];
$html = preg_split('/\r\n/', $_GET['html']);

foreach ($html as $value) {
    if (strpos(trim($value), "<div") === 0) {
        $matches = preg_match_all('/(\s*(id|class)\s*=\s*"(\w+)")/', $value, $arr);

        if (in_array(trim($arr[3][0]), $semantic)) {
            $returnValue = preg_replace('/(\s*?(id|class)\s*=\s*"(\w+)")\s*?/', '', $value);
            $returnValue = preg_replace('/" >/', '">', $returnValue);
            $returnValue = preg_replace('/ >/', '>', $returnValue);
            $returnValue = preg_replace('/[\s+]{2,}/', ' ', $returnValue);

            $newTag = str_replace('<div', '<' . $arr[3][0], $returnValue);
            echo $newTag . "\n";
        } else {
            echo $value . "\n";
        }
    } else if (strpos(trim($value), "</div>") === 0) {
        $match = preg_match('/(<!--\s*)(main|header|nav|article|section|aside|footer)(\s*-->)/', $value, $arrET);

        if ($match !== 0) {
            $val = preg_replace('/\s*(<!--\s*)(main|header|nav|article|section|aside|footer)(\s*-->)\s*/', null, $value);
            echo str_replace('</div>', '</' . $arrET[2] . '>', $val) . "\n";
        } else {
            echo $value . "\n";
        }
    } else {
        echo $value . "\n";
    }
}