Work around open_basedir redirections when overwriting inherited FDs

Author: clue

src/Factory.php

@@ -254,11 +254,12 @@ private function openProcessIo($filename, $flags = null)
             \defined('STDERR') ? \STDERR : \fopen('php://stderr', 'w')
         );
 
-        // do not inherit open FDs by explicitly overwriting existing FDs with dummy files
+        // do not inherit open FDs by explicitly overwriting existing FDs with dummy files.
+        // Accessing /dev/null with null spec requires PHP 7.4+, older PHP versions may be restricted due to open_basedir, so let's reuse STDERR here.
         // additionally, close all dummy files in the child process again
         foreach ($fds as $fd) {
             if ($fd > 2) {
-                $pipes[$fd] = array('file', '/dev/null', 'r');
+                $pipes[$fd] = \PHP_VERSION_ID >= 70400 ? ['null'] : $pipes[2];
                 $command .= ' ' . $fd . '>&-';
             }
         }

tests/FunctionalExampleTest.php

@@ -31,13 +31,20 @@ public function testQueryExampleExecutedWithCgiReturnsDefaultValueAfterContentTy
         $this->assertStringEndsWith("\r\n\r\n" . 'value' . PHP_EOL . '42' . PHP_EOL, $output);
     }
 
-    public function testQueryExampleWithOpenBasedirRestrictedRunsDefaultPhpAndReturnsDefaultValue()
+    public function testQueryExampleWithOpenBasedirRestrictedReturnsDefaultValue()
     {
-        if (!$this->canExecute('php --version')) {
-            $this->markTestSkipped('Unable to execute "php"');
+        $output = $this->execExample(escapeshellarg(PHP_BINARY) . ' -dopen_basedir=' . escapeshellarg(dirname(__DIR__)) . ' query.php');
+
+        $this->assertEquals('value' . PHP_EOL . '42' . PHP_EOL, $output);
+    }
+
+    public function testQueryExampleWithOpenBasedirRestrictedAndAdditionalFileDescriptorReturnsDefaultValue()
+    {
+        if (DIRECTORY_SEPARATOR === '\\') {
+            $this->markTestSkipped('Not supported on Windows');
         }
 
-        $output = $this->execExample(escapeshellarg(PHP_BINARY) . ' -dopen_basedir=' . escapeshellarg(dirname(__DIR__)) . ' query.php');
+        $output = $this->execExample(escapeshellarg(PHP_BINARY) . ' -dopen_basedir=' . escapeshellarg(dirname(__DIR__)) . ' query.php 3</dev/null');
 
         $this->assertEquals('value' . PHP_EOL . '42' . PHP_EOL, $output);
     }