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run code in 300+ PHP versions simultaneously
<?php $_SESSION['fr_nick'] = null; var_dump( [ isset( $_SESSION['fr_nick'] ), array_key_exists('fr_nick', $_SESSION), empty( $_SESSION['fr_nick'] ) ] );
Output for 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 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 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
array(3) { [0]=> bool(false) [1]=> bool(true) [2]=> bool(true) }
preferences:
279.08 ms | 404 KiB | 331 Q