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run code in 150+ php & hhvm versions
Bugs & Features
<?php var_dump(is_callable('f')); $a = null; call_user_func($a);
Output for 5.3.0 - 7.1.0
bool(false) Warning: call_user_func() expects parameter 1 to be a valid callback, no array or string given in /in/mTp3J on line 4
Output for 4.3.2 - 5.2.17
bool(false) Warning: call_user_func(): First argument is expected to be a valid callback in /in/mTp3J on line 4
Output for 4.3.0 - 4.3.1
bool(false) Warning: call_user_func() [http://www.php.net/function.call-user-func]: First argument is expected to be a valid callback in /in/mTp3J on line 4