<?php
function stringToRandomClass($str, $max = 10) {
    $hash = crc32($str);
    $number = ($hash % $max) + 1;
    return "random$number";
}

$content = "Hello";
$randomClass = stringToRandomClass(substr($content, 0, 4));
?>

<div class="<?= $randomClass ?>"><?= htmlspecialchars($content) ?></div>