PHP script only allow traffic from a certain domain?

Is there a simple script that would on开发者_开发问答ly allow visitors if they originate from a website of my choice?

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Checking the referrer is the most reliable way to accomplish this, but you should be aware that not all user agents (aka browsers) send a complete or correct referrer.

Something like this:

$target_site = 'http://www.google.com';
if (isset($_SERVER['HTTP_REFERER']) && preg_match("/$target_site/",$_SERVER['HTTP_REFERER'])) {
  // do something with people from google.com
} else {
  // do something else with everyone else
}

Read more about it: http://www.electrictoolbox.com/php-http-referer-variable/

PHP manual on $_SERVER superglobal: http://php.net/manual/en/reserved.variables.server.php

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You can use the $_SERVER['http_referer'] but that can be easily faked.

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If you get their referrer information you could check it against a list of accepted website origins and redirect them back to the site they came from if you don't want them.

$_SERVER["HTTP_REFERER"]