Find subdomain using regex in PHP

Question

Sorry if this is too small to be suitable as a stack overflow issue, but I'm a little used to regular expressions.

My question is: what is a regular expression that returns the string “token” for all the examples below?

• token.domain.com
• token.domain.com/
• token.domain.com/index.php
• token.domain.com/folder/index.php
• token.domain.com/folder/subfolder
• token.domain.com/folder/subfolder/index.php
• (added after editing)
• domain.com
• domain.com/

I am trying to use the preg_replace function inside to find out the subdomain of the current page from the variable $ _SERVER ['SERVER_NAME'].

Thanks in advance, Titel

: sebnow, , , , , - - , NULL

Answer 1

preg_replace('/^(?:([^\.]+)\.)?domain\.com$/', '\1', $_SERVER['SERVER_NAME'])

: :

<?php
    echo preg_replace('/^(?:([^\.]+)\.)?domain\.com$/', '\1', "sean.domain.com") . "<br />";
    echo preg_replace('/^(?:([^\.]+)\.)?domain\.com$/', '\1', "titel.domain.com") . "<br />";
    echo preg_replace('/^(?:([^\.]+)\.)?domain\.com$/', '\1', "domain.com") . "<br />";
?>

Answer 2

() :

^([^.]+)\..*$

, . :

list($subdomain, $rest) = explode('.', $_SERVER['SERVER_NAME'], 2);

Answer 3

preg_replace(), :

preg_replace('/\..*/', '', $_SERVER['SERVER_NAME'])

Answer 4

preg_match('@^([a-zA-Z0-9]*\.)?([a-zA-Z0-9]+)\.([a-zA-Z]{2,4})$@',$_SERVER["HTTP_HOST"], $matches);