Fiber::getCurrent() will only return true if you call it from within a Fiber while it is running.<?php$fiber = new Fiber(function () { echo "Inside Fiber. getCurrent: "; var_dump(Fiber::getCurrent()); // Here is object(Fiber)#1 (0) { } Fiber::suspend(); echo "Inside Fiber again after resume(). getCurrent: "; var_dump(Fiber::getCurrent()); // object(Fiber)#1 (0) { } again});echo "Before Fiber launch. getCurrent: ";var_dump($fiber->getCurrent()); // Here is NULL $fiber->start();echo "After suspend. getCurrent: ";var_dump($fiber->getCurrent()); // Here is NULL $fiber->resume();echo "After resume. getCurrent: ";var_dump($fiber->getCurrent()); // Here is NULL ?>Result:Before Fiber launch. getCurrent: NULLInside Fiber. getCurrent: object(Fiber)#1 (0) {}After suspend. getCurrent: NULLInside Fiber again after resume(). getCurrent: object(Fiber)#1 (0) {}After resume. getCurrent: NULL