Merge fiber switching functions

Zend/tests/fibers/fiber-status.phpt

@@ -10,6 +10,18 @@ $fiber = new Fiber(function (): void {
     var_dump($fiber->isRunning());
     var_dump($fiber->isSuspended());
     var_dump($fiber->isTerminated());
+
+    $nested = new Fiber(function () use ($fiber): void {
+        echo "\nWithin Nested Fiber:\n";
+        var_dump($fiber->isStarted());
+        var_dump($fiber->isRunning());
+        var_dump($fiber->isSuspended());
+        var_dump($fiber->isTerminated());
+        Fiber::suspend();
+    });
+
+    $nested->start();
+
     Fiber::suspend();
 });
 
@@ -49,6 +61,12 @@ bool(true)
 bool(false)
 bool(false)
 
+Within Nested Fiber:
+bool(true)
+bool(true)
+bool(false)
+bool(false)
+
 After Start:
 bool(true)
 bool(false)

Zend/tests/fibers/resume-previous-fiber.phpt

@@ -0,0 +1,28 @@
+--TEST--
+Resume previous fiber
+--FILE--
+<?php
+
+$fiber = new Fiber(function (): void {
+    $fiber1 = Fiber::this();
+
+    $fiber2 = new Fiber(function () use ($fiber1): void {
+        $fiber1->resume();
+    });
+
+    $fiber2->start();
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot resume a fiber that is not suspended in %sresume-previous-fiber.php:%d
+Stack trace:
+#0 %sresume-previous-fiber.php(%d): Fiber->resume()
+#1 [internal function]: {closure}()
+#2 %sresume-previous-fiber.php(%d): Fiber->start()
+#3 [internal function]: {closure}()
+#4 %sresume-previous-fiber.php(%d): Fiber->start()
+#5 {main}
+  thrown in %sresume-previous-fiber.php on line %d