Specific domain URL validation with Regular Expression

Question

I've been trying myself, and searching online, to write this regular expression but without success.

I need to validate that a given URL is from a specific domain and a well-formed link (in PHP). For example:

Good Domain: example.com

So good URLs from example.com:

So bad URLs not from example.com:

Some notes: I don't care about "http" verus "https" but if it matters to you assume "http" always The code that will use this regex is PHP so extra points for that.

UPDATE 2010:

Gruber adds a great URL regex:

?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))

See his post: An Improved Liberal, Accurate Regex Pattern for Matching URLs

Your "Good Domain" example is not a valid URL (missing path). — Nikolai Ruhe
– Nikolai Ruhe, Commented Jul 2, 2009 at 14:04
@Nikolar Ruhe: The path actually is optional: "http://" hostport [ "/" hpath [ "?" search ]] (see RFC 1738) — Gumbo
– Gumbo, Commented Jul 2, 2009 at 14:07
That's not indicating a valid URL, rather it is indicating the valid domain used by the example URLs but maybe I should just say 'blah.com' and no more. Either way, I think the point is made. — donohoe
– donohoe, Commented Jul 2, 2009 at 14:08

D. Evans · Accepted Answer · 2009-07-02 14:17:46Z

7

Do you have to use a regex? PHP has a lot of built in functions for doing this kind of thing.

filter_var($url, FILTER_VALIDATE_URL)

will tell you if a URL is valid, and

    $domain = parse_url($url, PHP_URL_HOST);

will tell you the domain it refers to.

It might be clearer and more maintainable than some mad regex.

answered Jul 2, 2009 at 14:17

D. Evans

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Peter Bailey · Accepted Answer · 2009-07-02 14:44:38Z

5

My stab at it

<?php

$pattern = "#^https?://([a-z0-9-]+\.)*blah\.com(/.*)?$#";

$tests = array(
    'http://blah.com/so/this/is/good'
  , 'http://blah.com/so/this/is/good/index.html'
  , 'http://www.blah.com/so/this/is/good/mice.html#anchortag'
  , 'http://anysubdomain.blah.com/so/this/is/good/wow.php'
  , 'http://anysubdomain.blah.com/so/this/is/good/wow.php?search=doozy'
  , 'http://any.sub-domain.blah.com/so/this/is/good/wow.php?search=doozy' // I added this case
  , 'http://999.sub-domain.blah.com/so/this/is/good/wow.php?search=doozy' // I added this case
  , 'http://obviousexample.com'
  , 'http://bbc.co.uk/blah.com/whatever/you/get/the/idea'
  , 'http://blah.com.example'
  , 'not/even/a/blah.com/url'
);

foreach ( $tests as $test )
{
  if ( preg_match( $pattern, $test ) )
  {
    echo $test, " <strong>matched!</strong><br>";
  } else {
    echo $test, " <strong>did not match.</strong><br>";
  }
}

//  Here's another way
echo '<hr>';
foreach ( $tests as $test )
{
  if ( $filtered = filter_var( $test, FILTER_VALIDATE_URL ) )
  {
    $host = parse_url( $filtered, PHP_URL_HOST );
    if ( $host && preg_match( "/blah\.com$/", $host ) )
    {
      echo $filtered, " <strong>matched!</strong><br>";
    } else {
      echo $filtered, " <strong>did not match.</strong><br>";
    }
  } else {
    echo $test, " <strong>did not match.</strong><br>";
  }
}

edited Jul 2, 2009 at 14:44

answered Jul 2, 2009 at 14:13

Peter Bailey

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4 Comments

D. Evans Over a year ago

The docs for the parse_url function state that it isn't meant to validate URLs: invalid URLs may still get parsed. So you need some additional checks.

Peter Bailey Over a year ago

Oh, I agree - it probably needs more rigorous testing. Still, my regex solution works just as well.

Peter Bailey Over a year ago

I adopted the logic of your post into my 2nd algo. Seems to work well!

suitedupgeek Over a year ago

Brilliant Peter :) - exactly what I was looking for.

Douglas Leeder · Accepted Answer · 2009-07-02 14:53:20Z

1

Perhaps:

^https?://[^/]*blah\.com(|/.*)$

Edit:

Protect against http://editblah.com

^https?://(([^/]*\.)|)blah\.com(|/.*)$

edited Jul 2, 2009 at 14:53

answered Jul 2, 2009 at 14:16

Douglas Leeder

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1 Comment

Peter Bailey Over a year ago

Close! But this would false positive a domain like fooblah.com

Jeremy Stein · Accepted Answer · 2009-07-02 14:10:07Z

0

\b(https?)://([-A-Z0-9]+\.)*blah.com(/[-A-Z0-9+&@#/%=~_|!:,.;]*)?(\?[A-Z0-9+&@#/%=~_|!:,.;]*)?

answered Jul 2, 2009 at 14:10

Jeremy Stein

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1 Comment

Douglas Leeder Over a year ago

I think that would allow blah.com.evil.domain (assuming the A-Z is A-Za-z)

chaos · Accepted Answer · 2009-07-02 14:12:55Z

0

!^https?://(?:[a-zA-Z0-9-]+\.)*blah\.com(?:/[^#]*(?:#[^#]+)?)?$!

answered Jul 2, 2009 at 14:12

chaos

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