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<?php $bar = range(0, 5); $i = 0; var_dump(array_keys($foo[$i] = $bar[$i++])[0]);
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, int given in /in/80dPM:5 Stack trace: #0 /in/80dPM(5): array_keys(0) #1 {main} thrown in /in/80dPM on line 5
Process exited with code 255.
Output for 7.4.0 - 7.4.33
Warning: array_keys() expects parameter 1 to be array, int given in /in/80dPM on line 5 Notice: Trying to access array offset on value of type null in /in/80dPM on line 5 NULL
Output for 7.3.16 - 7.3.33
Warning: array_keys() expects parameter 1 to be array, int given in /in/80dPM on line 5 NULL
Output for 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33
Warning: array_keys() expects parameter 1 to be array, integer given in /in/80dPM on line 5 NULL
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/80dPM on line 5
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/80dPM on line 5
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/80dPM on line 5
Process exited with code 255.

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