added test to clearly show distinction between unset (aka unmatched) subpattern and an empty match

Author: cmb69

ext/pcre/tests/bug61780.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Bug #61780 (Inconsistent PCRE captures in match results): basics
+--FILE--
+<?php
+preg_match('/(a)?([a-z]*)(\d*)/', '123', $matches);
+var_dump($matches);
+?>
+--EXPECT--
+array(4) {
+  [0]=>
+  string(3) "123"
+  [1]=>
+  NULL
+  [2]=>
+  string(0) ""
+  [3]=>
+  string(3) "123"
+}