mibo

$content = '<div class="text"><p>Some text, some text, some text</p></div>';
$newcontent = preg_replace("/<p[^>]*?>/", "<div>", $content);
$newcontent = str_replace("</p>", "</div>", $newcontent);

.text {
    -webkit-column-count: 3;
    -moz-column-count: 3;
    column-count: 3;
    -webkit-column-gap: 40px;
    -moz-column-gap: 40px;
    column-gap: 40px;
}