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<?php $data = [1 => true]; next($data); var_dump(key($data)); $data[0] = true; var_dump(key($data));
based on BANvA
Output for 7.3.0 - 7.3.23, 7.4.0 - 7.4.11, 8.0.0alpha1 - rc2
NULL NULL
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 - 7.1.32, 7.2.0 - 7.2.33
NULL int(0)
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/DoFve on line 2
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/DoFve on line 2
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/DoFve on line 2
Process exited with code 255.