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<?php function array_keys_recursive(array $array) : array { foreach ($array as $key => $value) { if (is_array($value)) { $index[$key] = array_keys_recursive($value); } else { $index []= $key; } } return $index ?? []; } $a = ['a'=>11, 'b'=>2,'c'=>['r'=>5,'s'=>8]]; $b = ['a'=>1, 'b'=>2, 'c'=>['r'=>15,'s'=>18]]; var_dump(array_keys_recursive($a) === array_keys_recursive($b)); $a = ['a'=>11, 'b'=>2,'c'=>['r'=>5,'s'=>8]]; $b = ['a'=>1, 'c'=>2, 'b'=>['r'=>15,'s'=>18]]; var_dump(array_keys_recursive($a) === array_keys_recursive($b)); $a = ['a'=>11, 'b'=>2,'c'=>['r'=>5,'s'=>8]]; $b = ['a'=>1, 'b'=>2, 'c'=>['r1'=>15,'m'=>18]]; var_dump(array_keys_recursive($a) === array_keys_recursive($b));