<?php
$test = "hello www.domain1.com and http://domain2.com or https://domain3.com/asdf and domain4.com/file.html orwww.domain5.com/file.html\n";
echo $test;
echo preg_replace("/((http(s?):\/\/)|(www\.))([A-Za-z0-9\/%#&=\.-_]+)/","<a href=\"http\\3://\\4\\5\">\\4\\5</a>", $test);
?>
outputs:
hello www.domain1.com and http://domain2.com or https://domain3.com/asdf and domain4.com/file.html or www.domain5.com/file.html
hello <a href="http://www.domain1.com">www.domain1.com</a> and <a href="http://domain2.com">domain2.com</a> or<a href="https://domain3.com/asdf">domain3.com/asdf</a> and domain4.com/file.html or <a href="http://www.domain5.com/file.html">www.domain5.com/file.html</a>