add a version check, the third argument in getopt requires PHP >= 7.1

bin/migrate

@@ -10,6 +10,10 @@ require PATH . 'vendor' . DIRECTORY_SEPARATOR . 'autoload.php';
 use PrivateBin\Configuration;
 use PrivateBin\Model;
 
+// third argument in getopt requires PHP >= 7.1
+if (version_compare(PHP_VERSION, '7.1.0') < 0) {
+    dieerr('migrate requires php 7.1 or above to work. Sorry.');
+}
 
 $longopts = array(
     "delete-after",

tst/MigrateTest.php

@@ -54,6 +54,10 @@ class MigrateTest extends PHPUnit_Framework_TestCase
 
     public function testMigrate()
     {
+        if (version_compare(PHP_VERSION, '7.1.0') < 0) {
+            return; // skip test on unsupported PHP versions
+        }
+
         $this->_model_1->delete(Helper::getPasteId());
         $this->_model_2->delete(Helper::getPasteId());