Conditional patterns in Regular expression in PHP

PHP code:


$phoneno = array(
"413 222 6859",
"4-(413)-222-6859",
"(413-222-6859",
"(413).222.6859",
"413 22 6859");


foreach ($phoneno as $number) {
echo "$number : ";


if (preg_match("/^


(1[-\s.])? # optional '1-', '1.' or '1'
( \( )? # optional opening parenthesis
\d{3} # the area code
(?(2) \) ) # if there was opening parenthesis, close it
[-\s.]? # followed by '-' or '.' or space
\d{3} # first 3 digits
[-\s.]? # followed by '-' or '.' or space
\d{4} # last 4 digits


$/x",$number)) {  # x to ignore white spaces in pattern


echo "valid\n";
} else {
echo "invalid\n";
}
}


Output:


413 222 6859 : valid
4-(413)-222-6859 : valid
(413-222-6859 : invalid
(413).222.6859 : valid
413 22 6859 : invalid