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<?php $a = array('dupa' => 2, 'zupa' => 3); unset($a['dupa']); var_dump($a);
Output for 4.3.1 - 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 - 5.6.22, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.29 - 7.2.33, 7.3.12 - 7.3.30, 7.4.0 - 7.4.23, 8.0.0 - 8.0.11, 8.1rc1 - rc2
array(1) { ["zupa"]=> int(3) }

preferences:
51.75 ms | 462 KiB | 5 Q