New test for file_exists (bug #39863). It currently xfail's

ext/standard/tests/file/bug39863.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Bug #39863 (file_exists() silently truncates after a null byte)
+--CREDITS--
+Andrew van der Stock, vanderaj @ owasp.org
+--FILE--
+<?php
+
+$filename = __FILE__ . chr(0). ".ridiculous";
+
+if (file_exists($filename)) {
+    echo "FAIL\n";
+}
+else {
+    echo "PASS\n";
+}
+?>
+===DONE===
+<?php exit(0); ?>
+--XFAIL--
+Needs bug #39863 fixed
+--EXPECT--
+PASS
+===DONE===
+