<?php $comment = preg_replace('/@([^(@|\s)]+)/', '<a href="/$1">@$1</a>','@name1 kdfjd fkjd as@name2 @ lkjlkj @name3'); ?>
Standard input is empty
string(105) "<a href="/name1">@name1</a> kdfjd fkjd as<a href="/name2">@name2</a> @ lkjlkj <a href="/name3">@name3</a>"