Bug->Doc #76104 [Opn->Ver]: Generator::next() causes yield to return null

Edit report at https://bugs.php.net/bug.php?id=76104&edit=1 ID: 76104 Updated by: requinix@php.net Reported by: alexey at kopytko dot com -Summary: foreach over a generator with an intermit send() works unexpectedly +Summary: Generator::next() causes yield to return null -Status: Open +Status: Verified -Type: Bug +Type: Documentation Problem Package: Scripting Engine problem PHP Version: 7.2.3 Block user comment: N Private report: N New Comment: next() and send() both advance the generator. That's how generators work. Using next(), explicitly or implicitly, means there's no way to pass a value back through the yield and thus the code will get null - just like when trying to get the return value from a function that doesn't return anything. Previous Comments: ------------------------------------------------------------------------ [2018-03-16 06:44:11] alexey at kopytko dot com Description: ------------ foreach calls next() on a generator, which for some reason triggers send(null) on the generator. All previous versions are also affected: https://3v4l.org/bfg64#v560 First reported here: https://stackoverflow.com/q/37817315 Test script: --------------- $generator = (function () { for ($i = 0; $i < 5; $i += 1) { $answer = (yield $i * 2); echo "received: $answer\n"; } })(); foreach ($generator as $x) { echo "sending $x\n"; $generator->send($x); } Expected result: ---------------- sending 0 received: 0 sending 2 received: 2 sending 4 received: 4 sending 6 received: 6 sending 8 received: 8 Actual result: -------------- sending 0 received: 0 received: sending 4 received: 4 received: sending 8 received: 8 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=76104&edit=1