toPHP() regression tests for bson_reader_read() errors

These test cases are derived from PHPC-615.

Author: jmikola

tests/bson/bson-toPHP_error-003.phpt

@@ -0,0 +1,28 @@
+--TEST--
+BSON\toPHP(): BSON decoding exceptions for malformed documents
+--SKIPIF--
+<?php require __DIR__ . "/../utils/basic-skipif.inc"?>
+--FILE--
+<?php
+require_once __DIR__ . "/../utils/basic.inc";
+
+$tests = array(
+    pack('Vx', 4), // Empty document with invalid length (too small)
+    pack('Vx', 6), // Empty document with invalid length (too large)
+);
+
+foreach ($tests as $bson) {
+    echo throws(function() use ($bson) {
+        toPHP($bson);
+    }, 'MongoDB\Driver\Exception\UnexpectedValueException'), "\n";
+}
+
+?>
+===DONE===
+<?php exit(0); ?>
+--EXPECTF--
+OK: Got MongoDB\Driver\Exception\UnexpectedValueException
+Could not read document from BSON reader
+OK: Got MongoDB\Driver\Exception\UnexpectedValueException
+Could not read document from BSON reader
+===DONE===