$re = '/(([A-Za-z]{3,9}:(?:\/\/)?(?:[-;:&=\+\$,\w]+@)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+@)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%@.\w_]*)#?(?:[\w]*))?)/';
$str = 'asdf
http://google.com/
asfd
http://yahoo.com/logo.jpg
http://www.apple.com/sdfsd.php?page_id=13&id=18210&status=active#1
http://youtube.com/logo.png';
$subst = "<a href=\"$1\">$1</a>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php