$re = '/\(?(\d{3})\)?[ -.]?(\d{3})[ -.]?(\d{4})/';
$str = '(123)456-7890 (321)-654-0987
(111) 111-1111
222-222-2222
(333)333.3333
(444).444.4444
blah blah blah (555) 555.5555
666.666.6666 random text';
$subst = "(\1)\2-\3";
$result = preg_replace($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