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<?php $x=new stdClass(); $y='1002'; $x->$y = ''; var_dump(key(array(1002=>'')), key((array)$x));
Output for 4.4.1, 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
int(1002) int(1002)
Output for 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.38, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33
int(1002) string(4) "1002"
Output for 4.3.2 - 4.3.11, 4.4.0, 4.4.2 - 4.4.9, 5.0.0 - 5.0.5
Fatal error: Only variables can be passed by reference in /in/blt2W on line 7
Process exited with code 255.
Output for 4.3.0 - 4.3.1
Fatal error: Only variables can be passed by reference in /in/blt2W on line 7

preferences:
272.4 ms | 401 KiB | 452 Q