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run code in 200+ php & hhvm versions
Bugs & Features
<?php var_dump(strtoupper(NULL));
Output for 5.6.0 - 5.6.30, 7.0.0 - 7.3.0rc3
string(0) ""
Output for hhvm-3.15.4
Warning: strtoupper() expects parameter 1 to be string, null given in /in/duiid on line 3 NULL