reflection: Test ReflectionFunction::__toString() with bound variables (#20608)

ext/reflection/tests/ReflectionFunction__toString_bound_variables.phpt

@@ -0,0 +1,32 @@
+--TEST--
+ReflectionFunction::__toString() with bound variables
+--FILE--
+<?php
+
+$closure_without_bounds = fn () => 0;
+
+$rf = new ReflectionFunction($closure_without_bounds);
+echo (string) $rf;
+
+$global = "";
+$closure_with_bounds = function() use($global) {
+    static $counter = 0;
+    return $counter++;
+};
+
+$rf = new ReflectionFunction($closure_with_bounds);
+echo (string) $rf;
+
+?>
+--EXPECTF--
+Closure [ <user> function {closure:%s:%d} ] {
+  @@ %sReflectionFunction__toString_bound_variables.php 3 - 3
+}
+Closure [ <user> function {closure:%s:%d} ] {
+  @@ %sReflectionFunction__toString_bound_variables.php 9 - 12
+
+  - Bound Variables [2] {
+      Variable #0 [ $global ]
+      Variable #1 [ $counter ]
+  }
+}