3v4l.org

run code in 300+ PHP versions simultaneously
<?php $test = array( 'abc' => 123, 'def' => 456, 'test' => array( 123 => 'hip', 'hop' => array( 'tip' => 'top', 'top' => null ) ) ); foreach ($test as $old => $arr) { if (is_array($arr)) { unset($test[$old]); foreach ($arr as $new => $v) { $test[$old.$new] = $v; } } } var_dump($test);
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 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.23, 8.2.0 - 8.2.10
array(4) { ["abc"]=> int(123) ["def"]=> int(456) ["test123"]=> string(3) "hip" ["testhop"]=> array(2) { ["tip"]=> string(3) "top" ["top"]=> NULL } }

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