bug symfony#25567 [Process] Fix setting empty env vars (nicolas-grekas)

This PR was merged into the 3.3 branch.

Discussion
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[Process] Fix setting empty env vars

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#25564
| License       | MIT
| Doc PR        | -

Commits
-------

03adce2 [Process] Fix setting empty env vars

Author: nicolas-grekas

src/Symfony/Component/Process/Process.php

@@ -326,8 +326,16 @@ public function start(callable $callback = null/*, array $env = array()*/)
             // @see : https://bugs.php.net/69442
             $ptsWorkaround = fopen(__FILE__, 'r');
         }
+        if (defined('HHVM_VERSION')) {
+            $envPairs = $env;
+        } else {
+            $envPairs = array();
+            foreach ($env as $k => $v) {
+                $envPairs[] = $k.'='.$v;
+            }
+        }
 
-        $this->process = proc_open($commandline, $descriptors, $this->processPipes->pipes, $this->cwd, $env, $this->options);
+        $this->process = proc_open($commandline, $descriptors, $this->processPipes->pipes, $this->cwd, $envPairs, $this->options);
 
         if (!is_resource($this->process)) {
             throw new RuntimeException('Unable to launch a new process.');

src/Symfony/Component/Process/Tests/ProcessTest.php

@@ -1423,14 +1423,14 @@ public function testEnvBackupDoesNotDeleteExistingVars()
 
     public function testEnvIsInherited()
     {
-        $process = $this->getProcessForCode('echo serialize($_SERVER);', null, array('BAR' => 'BAZ'));
+        $process = $this->getProcessForCode('echo serialize($_SERVER);', null, array('BAR' => 'BAZ', 'EMPTY' => ''));
 
         putenv('FOO=BAR');
         $_ENV['FOO'] = 'BAR';
 
         $process->run();
 
-        $expected = array('BAR' => 'BAZ', 'FOO' => 'BAR');
+        $expected = array('BAR' => 'BAZ', 'EMPTY' => '', 'FOO' => 'BAR');
         $env = array_intersect_key(unserialize($process->getOutput()), $expected);
 
         $this->assertEquals($expected, $env);
@@ -1511,7 +1511,7 @@ public function testRawCommandLine()
 )
 
 EOTXT;
-        $this->assertSame($expected, $p->getOutput());
+        $this->assertSame($expected, str_replace('Standard input code', '-', $p->getOutput()));
     }
 
     public function provideEscapeArgument()