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PHP function to return the domain or subdomain from a given url

PHP code to return the domain name from a given url string

Here is a simple function which uses regular expression to find the domain name from a given url string.

Input to the function is the URL string.

Here is what the function does:

It check whether string is null. If null, function return false , Else it will pass the url string to a php builtin function parse_url(). This function parses the given URL and returns an associative array containing any of the various components of the URL that are present. Then the preg_match() is applied on "host" component of the component array,to grab the domain name.

Code is given below:

Function to return domain name in a url string


function get_domain_from_url($input_url)
if( trim($input_url)=="") return false
$parts = parse_url($input_url);
$domain = isset($parts['host']) ? $parts['host'] : '';
if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
return $regs['domain'];
return false;

// How to use the function?

$domain_name = get_domain_from_url("");

echo $domain_name;

// this will output

PHP Function to return all url components as an array
Inorder to retrive all the components (including file extension,domain name and subdomain name) as an array , we can use amodified version of above function. The unction will return an associative array with each element in the url.


function get_url_components($input_url)
if( trim($input_url)=="") return false
$parts = parse_url($input_url);
$domain = isset($parts['host']) ? $parts['host'] : '';
if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
$parts["domain_name"]= $regs['domain'];

if( $dot_pos!==false){

return $parts;

// How to use the function?

$url_parts = get_url_components("");


// this will output as            Array ( [scheme] => http [host] => [path] => /2011/10/sub-domain-tracking-and-cross-domain.html [query] => t=1 [domain_name] => [file_extension] => html )

// You can access subdomain name as
$subdomain = $url_parts['host'];

// You can access domain name as
$domain = $url_parts['domain_name'];

// You can access query string as
$query_str = $url_parts['query'];

// You can access file extension
$file_ext = $url_parts['file_extension'];


Syntax: int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )
Searches subject for a match to the regular expression given in pattern. If match found then $matches array is filled with the results of search. $matches[0] will contain the text that matched the full pattern. read more >>

Syntax: mixed parse_url ( string $url [, int $component = -1 ] )
Function parses a given URL string and returns the components as an associative array. It will return FALSE for Seriously malformed urls. You can also pass some PHP constants ( PHP_URL_SCHEME, PHP_URL_HOST, PHP_URL_PORT, PHP_URL_USER, PHP_URL_PASS, PHP_URL_PATH, PHP_URL_QUERY,PHP_URL_FRAGMENT or PHP_URL_PORT) as second parameter to retrive a specific component from more>>

To get the domain name or subdomain name you can simply use like this:
<?php echo(parse_url($Your_Url_String,PHP_URL_HOST)); ?>

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