note 99287 added to functions.anonymous

Watch out when 'importing' variables to a closure's scope -- it's easy to miss / forget that they are actually being *copied* into the closure's scope, rather than just being made available. So you will need to explicitly pass them in by reference if your closure cares about their contents over time: <?php $result = 0; $one = function() { var_dump($result); }; $two = function() use ($result) { var_dump($result); }; $three = function() use (&$result) { var_dump($result); }; $result++; $one(); // outputs NULL: $result is not in scope $two(); // outputs int(0): $result was copied $three(); // outputs int(1) ?> Another less trivial example with objects (what I actually tripped up on): <?php //set up variable in advance $myInstance = null; $broken = function() uses ($myInstance) { if(!empty($myInstance)) $myInstance->doSomething(); }; $working = function() uses (&$myInstance) { if(!empty($myInstance)) $myInstance->doSomething(); } //$myInstance might be instantiated, might not be if(SomeBusinessLogic::worked() == true) { $myInstance = new myClass(); } $broken(); // will never do anything: $myInstance will ALWAYS be null inside this closure. $working(); // will call doSomething if $myInstance is instantiated ?> ---- Server IP: 69.147.83.197 Probable Submitter: 94.194.100.108 ---- Manual Page -- http://www.php.net/manual/en/functions.anonymous.php Edit -- https://master.php.net/note/edit/99287 Del: integrated -- https://master.php.net/note/delete/99287/integrated Del: useless -- https://master.php.net/note/delete/99287/useless Del: bad code -- https://master.php.net/note/delete/99287/bad+code Del: spam -- https://master.php.net/note/delete/99287/spam Del: non-english -- https://master.php.net/note/delete/99287/non-english Del: in docs -- https://master.php.net/note/delete/99287/in+docs Del: other reasons-- https://master.php.net/note/delete/99287 Reject -- https://master.php.net/note/reject/99287 Search -- https://master.php.net/manage/user-notes.php