Add test for fixed bug #68992

ext/json/tests/bug68992.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Bug #68992 (json_encode stacks exceptions thrown by JsonSerializable classes)
+--SKIPIF--
+<?php
+if (!extension_loaded('json')) die('skip');
+?>
+--FILE--
+<?php
+
+class MyClass implements JsonSerializable {
+    public function jsonSerialize() {
+	    throw new Exception('Not implemented!');
+	}
+}
+$classes = [];
+for($i = 0; $i < 5; $i++) {
+    $classes[] = new MyClass();
+}
+
+try {
+    json_encode($classes);
+} catch(Exception $e) {
+    do {
+	    printf("%s (%d) [%s]\n", $e->getMessage(), $e->getCode(), get_class($e));
+	} while ($e = $e->getPrevious());
+}
+?>
+--EXPECT--
+Failed calling MyClass::jsonSerialize() (0) [Exception]
+Not implemented! (0) [Exception]