REGEX: Non-conditional match

Question

Tried to search for an already answered question but ... couldn't find anything. I'm trying to make a regex that will match ipv4 or ipv4:port

$regex_ipv4 = '((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))(?![\\d])';
$regex_integer = '(\\d+)';

$x = "123.123.123.123";
$x2 = $x . ":12345";

preg_match("/^(?<ipv4>".$regex_ipv4.")(:)(?<port>".$regex_integer.")$/is", $x, $matches1);
preg_match("/^(?<ipv4>".$regex_ipv4.")(:)(?<port>".$regex_integer.")$/is", $x2, $matches2);

print_r($matches1);
print_r($matches2);

returns:

Array
(
)
Array
(
    [0] => 123.123.123.123:12345
    [ipv4] => 123.123.123.123
    [1] => 123.123.123.123
    [2] => 123.123.123.123
    [3] => :
    [port] => 12345
    [4] => 12345
    [5] => 12345
)

How can I make unconditional match of (:)(?<port>".$regex_integer.") ?

Thank you!

It seems the code is working, the named groups capture what you need. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 28, 2016 at 14:50
I want this regex: "^(?<ipv4>".$regex_ipv4.")(:)(?<port>".$regex_integer.")$" to strictly match "ipv4" OR "ipv4:port" in one line — user3405598
– user3405598, Commented Feb 28, 2016 at 15:22
Try preg_match("/^(?<ipv4>".$regex_ipv4.")(?::(?<port>".$regex_integer."))?$/", $x, $matches); — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 28, 2016 at 15:47

Wiktor Stribiżew · Accepted Answer · 2016-02-28 15:52:09Z

You must be searching for an optional group at the end of the pattern. It can look like:

^(?<ipv4>((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))(?!\d))(?::(?<port>\d+))?$

See the regex demo

In your code, use

preg_match("/^(?<ipv4>".$regex_ipv4.")(?::(?<port>".$regex_integer."))?$/", $x, $matches);

Note that the capturing group around a : is redundant. (?: starts the non-capturing group, )? at the end of the regex closes the group and ? quantifier makes the regex engine match this group 1 or 0 times.

And to clean up the regex patterns, I'd suggest to remove redundant character class with just one symbol and redundant capture groups:

$regex_ipv4 = "((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))(?!\\d)";
$regex_integer = "\\d+";

And here is a complete PHP demo:

$regex_ipv4 = "((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))(?!\\d)";
$regex_integer = "\\d+";

$x = "123.123.123.123";
$x2 = $x . ":12345";

preg_match("/^(?<ipv4>".$regex_ipv4.")(?::(?<port>".$regex_integer."))?$/", $x, $matches);
preg_match("/^(?<ipv4>".$regex_ipv4.")(?::(?<port>".$regex_integer."))?$/", $x2, $matches2);

print_r($matches);
print_r($matches2);

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