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run code in 200+ php & hhvm versions
<?php $arr = ['a' => 1]; $arr['b'] = &$arr['a']; var_dump($arr); $arr['b'] = 'xiami'; var_dump($arr);
Output for 5.6.0 - 5.6.38, hhvm-3.18.5 - 3.22.0, 7.0.0 - 7.3.1
array(2) { ["a"]=> &int(1) ["b"]=> &int(1) } array(2) { ["a"]=> &string(5) "xiami" ["b"]=> &string(5) "xiami" }