3v4l.org

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<?php $main_domains = ['example.co.uk','example.com','example.org']; $sub_domains = ['sub.example.com','ftp.example.org','ftp.example.co.uk','mail.example.com']; $results = []; array_walk( $sub_domains, function($subdomain) use ($main_domains, &$results) { foreach ($main_domains as $domain) { // or however you're checking if (strpos($subdomain, $domain) !== false) { $results[$domain][] = $subdomain; } } } ); var_dump($results);
Output for 5.6.0 - 5.6.26, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
array(3) { ["example.com"]=> array(2) { [0]=> string(15) "sub.example.com" [1]=> string(16) "mail.example.com" } ["example.org"]=> array(1) { [0]=> string(15) "ftp.example.org" } ["example.co.uk"]=> array(1) { [0]=> string(17) "ftp.example.co.uk" } }

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164.77 ms | 404 KiB | 188 Q