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run code in 300+ PHP versions simultaneously
<?php $a = array('xml' => array( 'attributes' => array( 'version' => '1.0', 'encoding' => 'utf-8', ), )); $t = array('test' => 'my_test_123'); $a['xml']['attributes'] = array_merge($a['xml']['attributes'], $t); print_r($a);
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.36, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.12 - 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 - 8.3.6
Array ( [xml] => Array ( [attributes] => Array ( [version] => 1.0 [encoding] => utf-8 [test] => my_test_123 ) ) )

preferences:
269.78 ms | 406 KiB | 349 Q