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<?php $arr = [1=>[[100]], 2=>[[200]]]; $ref = &$arr[1]; $empty = [0]; $ref[] = array_merge($empty, [101]); var_dump($arr);
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, 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 - 8.3.6
array(2) { [1]=> &array(2) { [0]=> array(1) { [0]=> int(100) } [1]=> array(2) { [0]=> int(0) [1]=> int(101) } } [2]=> array(1) { [0]=> array(1) { [0]=> int(200) } } }
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/entHv on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected '[' in /in/entHv on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/entHv on line 3
Process exited with code 255.

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