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Asked: 2026-05-16T16:38:31+00:00

First lets define a URL according to my requirements. The only protocols optionally allowed

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First lets define a “URL” according to my requirements.

The only protocols optionally allowed are http:// and https://

then a mandatory domain name like stackoverflow.com

then optionally the rest of url components (path, query, hash, …)

For reference a list of valid and invalid url’s according to my requirements

VALID

INVALID

  • http://www (php filter_var allow this, yes i know is a valid url)
  • google
  • http://www..des (php filter_var allow this)
  • Any url with not allowed characters in the domain name

For completeness here is my php version: 5.3.2-1ubuntu4.2

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1 Answer

  1. Editorial Team

    As a starting point you can use this one, it’s for JS, but it’s easy to convert it to work for PHP preg_match.

    /^(https?\://)?(www\.)?([a-z0-9]([a-z0-9]|(\-[a-z0-9]))*\.)+[a-z]+$/i

    For PHP should work this one:

    $reg = '@^(https?\://)?(www\.)?([a-z0-9]([a-z0-9]|(\-[a-z0-9]))*\.)+[a-z]+$@i';

    This regexp anyway validates only the domain part, but you can work on this or split the url at the 1st slash '/' (after "://") and validate separately the domain part and the rest.

    BTW: It would validate also "http://www.domain.com.com" but this is not an error because a subdomain url could be like: "http://www.subdomain.domain.com" and it’s valid! And there is almost no way (or at least no operatively easy way) to validate for proper domain tld with a regex because you would have to write inline into your regex all possible domain tlds ONE BY ONE like this:

    /^(https?\://)?(www\.)?([a-z0-9]([a-z0-9]|(\-[a-z0-9]))*\.)+(com|it|net|uk|de)$/i

    (this last one for instance would validate only domain ending with .com/.net/.de/.it/.co.uk). New tlds always come out, so you would have to adjust you regex everytimne a new tld comes out, that’s a pain in the neck!

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