PHP - Efficient way to check if subdomain exists

Question

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PHP function to get the subdomain of a URL

Im looking for an efficient way to tell if a subdomain exists within a URL.

The domain name will always be fixed e.g. mydomin.com, however if a subdomain is not set, I need to redirect.

One thought I had is that if there is more than one period (.), a subdomain is set, but im not sure how to implement this.

Many thanks.

EDIT: Sorry for not being too clear. I do not have a current solution, but looking at other posts I can see several examples of how to get the subdomain e.g.

array_shift(explode(".",$_SERVER['HTTP_HOST']));

But i do not want the subdomain, just to check if one exists. The subdomain could be anything.

http://stackoverflow.com/questions/5292937/php-function-to-get-the-subdomain-of-a-url — xdazz, Oct 06 '12 at 10:58
Do you already have an **inefficient** solution? Usually programmers ask about something efficient when their current solution just doesn't fit the performance requirements. So, what's your *current* one? — zerkms, Oct 06 '12 at 11:00

score 1 · Answer 1 · answered Oct 06 '12 at 11:02

1

I would rather use apache rewrite engine (or any webserver rewrite process) :

# .htaccess file

RewriteCond %{HTTP_HOST} ^yourdomin\.com$
RewriteRule (.*) http://sub.yourdomin.com/$1 [R=301,L]

answered Oct 06 '12 at 11:02

Jean-Christophe Meillaud

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Sietse · Accepted Answer · 2013-06-19T16:05:56.190

1

You can get the hostname with parse_url. Then you break it down with explode():

function hasSubdomain($url) {
    $parsed = parse_url($url);
    $exploded = explode('.', $parsed["host"]);
    return (count($exploded) > 2);
}

On google you can find really easily how to redirect someone.

edited Jun 19 '13 at 16:05

answered Oct 06 '12 at 11:06

Sietse

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4
10

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What about `"someDomainName.co.uk"`? I wouldn't say that has a subdomain. But that would return `true` for this function no? – Tommy Bravo Jul 31 '14 at 09:45
Just check if count() is higher than 3, instead of 2. – Sietse Aug 01 '14 at 10:27
I guess this is the better answer: http://stackoverflow.com/a/288864/839332 But thanks anyway. – Tommy Bravo Aug 01 '14 at 12:57

PHP - Efficient way to check if subdomain exists

2 Answers2