Online PHP editor | output for 9OsSD

<?php $atcode = '11F5796B61690196'; $sub1 = [ '0' => '2', '1' => '3', '2' => '0', '3' => '1', '4' => '6', '5' => '7', '7' => '5', '8' => 'A', '9' => 'B', 'A' => '8', 'B' => '9', 'C' => 'E', 'D' => 'F', 'E' => 'C', 'F' => 'D' ]; var_export( preg_replace_callback( '/.*(.)(.)/', fn($m) => str_repeat(strtr($m[1], $sub1) . $m[2], 2), $atcode ) );