Question

I want if my visitors go to subdomain.example.com that they get redirected to anothersubdomain.example.com. And if they go to css.subdomain.example.com that they get redirected to css.anothersubdomain.example.com etc.

I’ve tried the following regexes (with preg_match):

Attempt 1:

if(preg_match('#(([\w\.-]+)\.subdomain|subdomain)\.example\.com#', $_SERVER['SERVER_NAME'], $match)) {
    header('Location: http://'.$match[1].'anothersubdomain.example.com/');
}

If they go to: subdomain.example.com they get redirected to: anothersubdomain.example.com

But If they go to: css.subdomain.example.com they get redirected also to: subdomain.example.com – So that is not working

Attempt 2:

if(preg_match('#([\w\.-]+)\.subdomain\.example\.com#', $_SERVER['SERVER_NAME'], $match)) {
    header('Location: http://'.$match[1].'.anothersubdomain.example.com/');
}

If they go to: css.subdomain.example.com they get redirected to: css.anothersubdomain.example.com

But If they go to: subdomain.example.com they get redirected to: .subdomain.example.com – And that URL is not valid so also this attempt is not working.

Somebody has an answer? I want not to use nginx or apache rewrites.

Thanks in advance.

Answer 1

This worked for me:

$tests = array(
    'subdomain.example.com' => 'anothersubdomain.example.com',
    'css.subdomain.example.com' => 'css.anothersubdomain.example.com'
);

foreach( $tests as $test => $correct_answer) {
    $result = preg_replace( '#(\w+\.)?subdomain\.example\.com#', '$1anothersubdomain.example.com', $test);
    if( strcmp( $result, $correct_answer) === 0) echo "PASS\n";
}

What I did is made the capturing group for the “first” subdomain optional. So, if you printed out the results like so:

foreach( $tests as $test => $correct_answer) {
        $result = preg_replace( '#(\w+\.)?subdomain\.example\.com#', '$1anothersubdomain.example.com', $test);
    echo 'Input:    ' . $test . "\n" . 
         'Expected: ' . $correct_answer . "\n" . 
         'Actual  : ' .$result . "\n\n";
}

You’d get as output:

Input:    subdomain.example.com
Expected: anothersubdomain.example.com
Actual  : anothersubdomain.example.com

Input:    css.subdomain.example.com
Expected: css.anothersubdomain.example.com
Actual  : css.anothersubdomain.example.com

Now to apply it to your needs:

if( preg_match( '#(\w+\.)?subdomain\.example\.com#', $_SERVER['SERVER_NAME'], $matches)) {
    echo header( 'Location: http://'. (isset( $matches[1]) ? $matches[1] : '') .'anothersubdomain.example.com/');
}