Regular expression required for valid domain name check in PHP

Question

I need a regular expression which will check the domain name including characters like a-z A-Z 0-9 -

Also does any domain name having underscore _ character?

Please help me.

no I did not. But working on one scenario where we should not allow domain name like www.platform.com/test. /test or ?test should not be allowed at all. — Umesh Kulkarni
– Umesh Kulkarni, Commented Jun 4, 2012 at 7:32
I meant to say there should be only domain name or domain name with subdomain. No other parts are allowed. — Umesh Kulkarni
– Umesh Kulkarni, Commented Jun 4, 2012 at 7:34

user1047248 · Accepted Answer · 2012-06-04 07:36:09Z

1

I guess this is what youre searching for:

^[a-zA-Z0-9]+([a-zA-Z0-9-.]+)?.(com|org|net|mil|edu|de|COM|ORG|NET|MIL|EDU|DE)$

answered Jun 4, 2012 at 7:36

user1047248

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5 Comments

Umesh Kulkarni Over a year ago

I guess it will not work as extension could be anything like .in or .co.in. I just wanted to make sure there should not be any slashes or any unwanted character. Only domain name should be there.

Hassan Khodadadeh Over a year ago

there are about 250 other top level domains

Hassan Khodadadeh Over a year ago

and you can add i modifier to your regex to prevent duplication!

Ed Daniel Over a year ago

Even more than that, with the advent of .companyname and similar TLDs. Having a whitelist of acceptable TLDs is never gonna work...

verisimilitude Over a year ago

@UmeshKulkarni: I feel using the above answers as a base, you should be able to work this up.

Miguel Pérez · Accepted Answer · 2012-06-04 08:11:13Z

1

This regular expression would work on any number of subdomains and all top level domains (the world is not just murka):

/^ (?: [a-z0-9] (?:[a-z0-9\-]* [a-z0-9])? \. )*  #Subdomains
   [a-z0-9] (?:[a-z0-9\-]* [a-z0-9])?            #Domain
   \. [a-z]{2,6} $                               #Top-level domain
/ix

Domain names cannot have underscores. Only [a-zA-Z0-9], as well as hyphens if they are not at the beginning or the end of a subdomain name.

answered Jun 4, 2012 at 8:11

Miguel Pérez

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2 Comments

Kevin Cox Over a year ago

DOMAIN names CAN have underscores. HOST NAMES can't. There is a difference and he is most likely worried about host names but I just thought I should point this out.

kdjernigan Over a year ago

What DOMAIN name can have underscore? I tried this..I went to godaddy, tried searching for e_s.com and it corrected it to es.com. Then, went into cPanel to try to add a subdomain with _, and it said it was invalid. Trying to figure out what DOMAIN name can have underscore? Are you referring to what comes after the /? Just trying to figure this out. Sorry to bring this back up. This post was helpful to me, so wanted to double check what you were referring to.

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