Regex matching only a portion of string

Question

I would like to match a portion of a URL in this order.

First the domain name will remain static. So, nothing check with regex.

$domain_name = "http://foo.com/";

What I would like to validate is what comes after the last /.

So, my AIM is to create something like.

$stings_only            = "[\w+]";
$number_only            = "[\d+]";
$numbers_and_strings    = "[0-9][a-z][A-Z]";

Now, I would like to just use the above variables to check if a URL confirms to the patterns mentioned.

$example_url = "http://foo.com/some-title-with-id-1"; 

var_dump(preg_match({$domain_name}{$strings_only}, $example_url));

The above should return false, because title is NOT $string_only.

$example_url = "http://foo.com/foobartar"; 

var_dump(preg_match({$domain_name}{$strings_only}, $example_url));

The above should return true, because title is $string_only.

1. You really need to read about using regex 2. You don't need regex for this problem. — anubhava
– anubhava, Commented May 14, 2014 at 21:25
@anubhava You don't understand. The /./ is just an example. It could also be \d+ or any other pattern. So, regex is needed — iOi
– iOi, Commented May 14, 2014 at 21:55

Sam · Accepted Answer · 2014-05-14 22:52:23Z

2

Update:

~^http://foo\.com/[a-z]+/?$~i
~^http://foo\.com/[0-9]+/?$~
~^http://foo\.com/[a-z0-9]+/?$~i

These would be your three expressions to match alphabetical URLs, numeric URLS, and alphanumeric. A couple notes, \w matches [a-zA-Z0-9_] so I don't think it is what you expected. The + inside of your character class ([]) does not have any special meaning, like you may expect. \w and \d are "shorthand character classes" and do not need to be within the [] syntax (however they can be, e.g. [\w.,]). Notice the i modifier, this makes the expressions case-insensitive so we do not need to use [a-zA-Z].

$strings_only = '~^http://foo\.com/[a-z]+/?$~i';

$url = 'http://foo.com/some-title-with-id-1';
var_dump(preg_match($strings_only, $url)); // int(0)

$url = 'http://foo.com/foobartar';
var_dump(preg_match($strings_only, $url)); // int(1)

Test/tweak all of my above expressions with Regex101.

. matches any character, but only once. Use .* for 0+ or .+ for 1+. However, these will be greedy and match your whole string and can potentially cause problems. You can make it lazy by adding ? to the end of them (meaning it will stop as soon as it sees the next character /). Or, you can specify anything but a / using a negative character class [^/].

My final regex of choice would be:

~^https://stolak\.ru/([^/]+)/?$~

Notice the ~ delimiters, so that you don't need to escape every /. Also, you need to escape the . with \ since it has a special meaning. I threw the [^/]+ URI parameter into a capture group and made the trailing slash optional by using /?. Finally, I anchored this to the beginning and the end of the strings (^ and $, respectively).

Your question was somewhat vague, so I tried to interpret what you wanted to match. If I was wrong, let me know and I can update it. However, I tried to explain it all so that you could learn and tweak it to your needs. Also, play with my Regex101 link -- it will make testing easier.

Implementation:

$pattern = '~^https://stolak\.ru/([^/]+)/?$~';
$url = 'https://stolak.ru/car-type-b1';

preg_match($pattern, $url, $matches);
var_dump($matches);

// array(2) {
//   [0]=>
//   string(29) "https://stolak.ru/car-type-b1"
//   [1]=>
//   string(11) "car-type-b1"
// }

edited May 14, 2014 at 22:52

answered May 14, 2014 at 21:27

Sam

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4 Comments

iOi Over a year ago

getting error Warning: preg_match(): No ending delimiter '~' found

Sam Over a year ago

You copied the expression wrong, make sure you have the ~ on both sides...see my PHP code in the edit.

iOi Over a year ago

Still this did not answer the problem. Thanks for the effort though.

Sam Over a year ago

Did you even read through my answer? Or just try to plug it in.. RE: "Your question was somewhat vague, so I tried to interpret what you wanted to match. If I was wrong, let me know and I can update it." -- update your question and I can help, no one else will be able to do anything better than a guess.

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