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run code in 200+ php & hhvm versions
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<?php $a = 0; function f(&$arg) { $arg++; } var_dump(f(1)); ?>
based on rSi4Q
Output for 5.6.38 - 7.3.0rc3
Fatal error: Only variables can be passed by reference in /in/mIjQp on line 7
Process exited with code 255.