PHP Regex not matching string as expected

Question

The Regex:

https?://([a-zA-Z0-9-_]{1,50}[.])*[a-zA-z0-9-_]{1,50}[.]([(org)(gov)(com)]{3}|[(us)(fi)]{2})

The Tester:

http://regex.powertoy.org/

The Code:

if(preg_match_all('|https?://([a-zA-Z0-9-_]{1,50}[.])*[a-zA-z0-9-_]{1,50}[.]([(org)(gov)(com)]{3}|[(us)(fi)]{2})|',$row['text'],$links))
    {
        print_r($links[0]);
        /*for($x=0;$x<count(links[0]);$x++)
        {
            $row['text'] = str_replace($links[0][$x], 'link' . $link[0][$x] . 'link', $row['text'];
        }*/
    }else{
        echo 'Failure!';
    }

The regex matches URLs in the tester fine, but not at all in an HTML/PHP front end. I'm not sure what the problem is. The point of the regex/code is basically to match URLs regardless of the number of subdomains.

What does the code look like and what input is not matching when it should? — jeroen
– jeroen, Commented Aug 16, 2012 at 14:43

Ωmega · Accepted Answer · 2012-08-16 14:50:49Z

2

Fix of your regex pattern is:

https?:\/\/(?:[\w-]{1,50}\.)*[\w-]{1,50}\.(?:org|gov|com|us|fi)

But I recommend to use:

https?:\/\/(?:[a-zA-Z\d]+(?:\-[a-zA-Z\d]+)*\.)+(?:org|gov|com|us|fi)

edited Aug 16, 2012 at 14:50

answered Aug 16, 2012 at 14:45

Ωmega

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jeroen · Accepted Answer · 2012-08-16 14:53:52Z

2

You are using the | character as your delimiter but you are also using it in your regex.

I would recommend using another character and making the regex case-insensitive to avoid problems like where you have for example a-zA-z:

preg_match_all('#https?://([a-zA-Z0-9-_]{1,50}[.])*[a-zA-z0-9-_]{1,50}[.]([(org)(gov)(com)]{3}|[(us)(fi)]{2})#i',$row['text'],$links)

answered Aug 16, 2012 at 14:53

jeroen

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4 Comments

Ωmega Over a year ago

There should be no underscore allowed in the domain name and dash character cannot be first or last character of (sub-)domain

jeroen Over a year ago

@Ωmega To be honest, I didn't really look at the regex itself, but mainly why it would work in the tester but not in php.

dualed Over a year ago

My vote up because you actually explained the problem of the pattern, though you don't need [a-zA-Z] if you use i pattern modifier

jeroen Over a year ago

@dualed True, that was kind of implied with the case-insensitivity. I would probably use \w and put the - at the beginning or the end to avoid it turning into a range as well.

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