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<?php $a = array( 'a' => array( 'A', 'B', 'C', 'D', ), 'b' => array( 'AA', 'BB', 'CC', 'DD', ), ); print_r($a[a]);
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Fatal error: Uncaught Error: Undefined constant "a" in /in/54IGP:12 Stack trace: #0 {main} thrown in /in/54IGP on line 12
Process exited with code 255.
Output for 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33
Warning: Use of undefined constant a - assumed 'a' (this will throw an Error in a future version of PHP) in /in/54IGP on line 12 Array ( [0] => A [1] => B [2] => C [3] => D )
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33
Notice: Use of undefined constant a - assumed 'a' in /in/54IGP on line 12 Array ( [0] => A [1] => B [2] => C [3] => D )

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276.47 ms | 402 KiB | 372 Q