<?php
$str = 'http://s...content-available-to-author-only...e.ru, http://s...content-available-to-author-only...e.com, https://s...content-available-to-author-only...e.info sgdf';
echo preg_replace('#\b(https?://)([a-z0-9-]+)\.([a-z]{2,})\b#', '<a href="$1$2.$3">$2.$3</a>', $str);
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