Compare strings and extract variables?

Question

Could someone tell me how I would do this. I have 3 strings.

$route = '/user/$1/profile/$2';
$path = '/user/profile/$1/$2';
$url = '/user/jason/profile/friends';

What I need to do is check to see if the url conforms to the route. I am trying to do this as follows.

$route_segments = explode('/', $route);
$url_segments = explode('/', $url);

$count = count($url_segments);
for($i=0; $i < $count; $i++) {
  if ($route_segments[$i] != $url_segments[$i] && ! preg_match('/\$[0-9]/', $route_segments[$i])) {
    return false;
  }
}

I assume the regex works, it's the first I have ever written by myself. :D

This is where I am stuck. How do I compare the following strings:

$route = '/user/$1/profile/$2';
$url = '/user/jason/profile/friends';

So I end up with:

array (
    '$1' => 'jason',
    '$2' => 'friends'
);

I assume that with this array I could then str_replace these values into the $path variable?

Brad Christie · Accepted Answer · 2010-11-24 16:43:19Z

1

$route_segments = explode('/',$route);
$url_segments = explode('/',$url);
$combined_segments = array_combine($route_segments,$url_segments);

Untested and not sure how it reacts with unequal array lengths, but that's probably what you're looking for regarding an element-to-element match. Then you can pretty much iterate the array and look for $ and use the other value to replace it.

EDIT

/^\x24[0-9]+$/

Close on the RegEx except you need to "Escape" the $ in a regex because this is a flag for end of string (thus the \x24). The [0-9]+ is a match for 1+ number(s). The ^ means match to the beginning of the string, and, as explained, the $ means match to the end. This will insure it's always a dollar sign then a number.

(actually, netcoder has a nice solution)

edited Nov 24, 2010 at 16:43

answered Nov 24, 2010 at 16:20

Brad Christie

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1 Comment

ComputerUser Over a year ago

I like this solution, its simple and to the point. Thanks for the tip on the regex.

Vincent Robert · Accepted Answer · 2010-11-24 16:25:03Z

1

I did something similar in a small framework of my own.

My solution was to transform the template URL: /user/$1/profile/$2

into a regexp capable of parsing parameters: ^\/user\/([^/]*)/profile/([^/]*)\/$

I then check if the regexp matches or not.

You can have a look at my controller code if you need to.

answered Nov 24, 2010 at 16:25

Vincent Robert

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2 Comments

ComputerUser Over a year ago

The main selling point of my little application is simplicity. I feel that this would go against this principle. Its a nice solution though thanks.

Vincent Robert Over a year ago

I think you misunderstood my argument. I was not suggesting that you ask your user to input regexp instead of your more natural language. I was suggesting that you transform your natural language URL pattern to regexp at runtime in order to match current URL more easily.

netcoder · Accepted Answer · 2010-11-24 16:34:08Z

1

You could do this:

$route = '/user/$1/profile/$2';
$path = '/user/profile/$1/$2';
$url = '/user/jason/profile/friends';

$regex_route = '#'.preg_replace('/\$[0-9]+/', '([^/]*)', $route).'#';
if (preg_match($regex_route, $url, $matches)) {
   $real_path = $path;
   for ($i=1; $i<count($matches); $i++) {
      $real_path = str_replace('$'.$i, $matches[$i], $real_path);
   }
   echo $real_path; // outputs /user/profile/jason/friends
} else {
   // route does not match
}

answered Nov 24, 2010 at 16:34

netcoder

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Comments

Gumbo · Accepted Answer · 2010-11-24 16:55:32Z

You could replace any occurrence of $n by a named group with the same number (?P<_n>[^/]+) and then use it as pattern for preg_match:

$route = '/user/$1/profile/$2';
$path = '/user/profile/$1/$2';
$url = '/user/jason/profile/friends';

$pattern = '~^' . preg_replace('/\\\\\$([1-9]\d*)/', '(?P<_$1>[^/]+)', preg_quote($route, '~')) . '$~';
if (preg_match($pattern, $url, $match)) {
    var_dump($match);
}

This prints in this case:

array(5) {
  [0]=>
  string(28) "/user/jason/profile/friends"
  ["_1"]=>
  string(5) "jason"
  [1]=>
  string(5) "jason"
  ["_2"]=>
  string(7) "friends"
  [2]=>
  string(7) "friends"
}

Using a regular expression allows you to use the wildcards at any position in the path and not just as a separate path segment (e.g. /~$1/ for /~jason/ would work too). And named subpatterns allows you to use an arbitrary order (e.g. /$2/$1/ works as well).

And for a quick fail you can additionally use the atomic grouping syntax (?>…).

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