vlucas · adam-prickett · Oct 10, 2016 · Oct 10, 2016
diff --git a/README.md b/README.md
@@ -217,6 +217,17 @@ VAR="value" # comment
 VAR=value # comment
 ```
 
+Configuration Flags
+-----------------------------
+
+You may enable or disable certain features by using configuration flags at
+the top of a .env file, before any variable declarations.
+
+```shell
+PHPDOTENV_NO_SET_ENV    # Prevents environment variables being set to the $_ENV superglobal
+PHPDOTENV_NO_SET_SERVER # Prevents environment variables being set to the $_SERVER superglobal
+```
+
 Usage Notes
 -----------
 

diff --git a/src/Loader.php b/src/Loader.php
@@ -28,6 +28,20 @@ class Loader
      */
     protected $immutable;
 
+    /**
+     * Array of config variables
+     *
+     * @var array
+     */
+    protected $configFlags = array();
+
+    /**
+     * Have we set an environment variable yet?
+     *
+     * @var bool
+     */
+    protected $hasSetEnvironmentVariable = false;
+
     /**
      * Create a new loader instance.
      *
@@ -54,6 +68,12 @@ public function load()
         $filePath = $this->filePath;
         $lines = $this->readLinesFromFile($filePath);
         foreach ($lines as $line) {
+            if (!$this->isComment($line) && $this->looksLikeConfigFlag($line)) {
+                if ($this->hasSetEnvironmentVariable) {
+                    throw new InvalidFileException('PHPDOTENV_ flags must appear before any environment variables are set');
+                }
+                $this->setConfigFlag($line);
+            }
             if (!$this->isComment($line) && $this->looksLikeSetter($line)) {
                 $this->setEnvironmentVariable($line);
             }
@@ -162,6 +182,18 @@ protected function looksLikeSetter($line)
         return strpos($line, '=') !== false;
     }
 
+    /**
+     * Determine if the given line looks like a config flag
+     *
+     * @param  string $line
+     *
+     * @return bool
+     */
+    protected function looksLikeConfigFlag($line)
+    {
+        return strpos(ltrim($line), 'PHPDOTENV_') === 0;
+    }
+
     /**
      * Split the compound string into parts.
      *
@@ -278,6 +310,23 @@ protected function sanitiseVariableName($name, $value)
         return array($name, $value);
     }
 
+    /**
+     * Removes EOL comments and santises config flag values
+     *
+     * @param  string $name
+     * @return string
+     */
+    protected function sanitiseConfigFlag($name)
+    {
+        // Remove EOL comments from flags
+        $parts = explode(' #', $name, 2);
+        $name = trim($parts[0]);
+
+        $name = trim(str_replace(array('export ', '\'', '"'), '', $name));
+
+        return $name;
+    }
+
     /**
      * Determine if the given string begins with a quote.
      *
@@ -327,6 +376,10 @@ public function getEnvironmentVariable($name)
      */
     public function setEnvironmentVariable($name, $value = null)
     {
+        if (!$this->hasSetEnvironmentVariable) {
+            $this->hasSetEnvironmentVariable = true;
+        }
+
         list($name, $value) = $this->normaliseEnvironmentVariable($name, $value);
 
         // Don't overwrite existing environment variables if we're immutable
@@ -345,8 +398,15 @@ public function setEnvironmentVariable($name, $value = null)
             putenv("$name=$value");
         }
 
-        $_ENV[$name] = $value;
-        $_SERVER[$name] = $value;
+        // Set the $_ENV superglobal if NO_SET_ENV flag has not been set
+        if (!$this->hasConfigFlag('NO_SET_ENV')) {
+            $_ENV[$name] = $value;
+        }
+
+        // Set the $_SERVER superglobal if NO_SET_SERVER flag has not been set
+        if (!$this->hasConfigFlag('NO_SET_SERVER')) {
+            $_SERVER[$name] = $value;
+        }
     }
 
     /**
@@ -378,4 +438,33 @@ public function clearEnvironmentVariable($name)
 
         unset($_ENV[$name], $_SERVER[$name]);
     }
+
+    /**
+     * Set a config variable to the $config array
+     *
+     * @param string $name
+     *
+     * @return void
+     */
+    public function setConfigFlag($name)
+    {
+        $name = $this->sanitiseConfigFlag($name);
+
+        // Remove the PHPDOTENV_ prefix
+        $name = substr($name, 10);
+
+        $this->configFlags[$name] = true;
+    }
+
+    /**
+     * Utility method to check for config flag being set
+     *
+     * @param  string  $name
+     *
+     * @return boolean
+     */
+    public function hasConfigFlag($name)
+    {
+        return (isset($this->configFlags[$name]));
+    }
 }
diff --git a/tests/Dotenv/DotenvTest.php b/tests/Dotenv/DotenvTest.php
@@ -327,4 +327,34 @@ public function testDotenvRequiredCanBeUsedWithoutLoadingFile()
         $dotenv->required('REQUIRED_VAR')->notEmpty();
         $this->assertTrue(true);
     }
+
+    public function testDotenvConfigFlagSets()
+    {
+        $dotenv = new Dotenv($this->fixturesFolder, 'flag.env');
+        $dotenv->load();
+
+        $this->assertEquals($_SERVER['CONFIG_SET'], 'true');
+        $this->assertEquals(getenv('CONFIG_SET'), 'true');
+        $this->assertTrue(!isset($_ENV['CONFIG_SET']));
+    }
+
+    public function testDotenvConfigFlagSetsWithEOLComment()
+    {
+        $dotenv = new Dotenv($this->fixturesFolder, 'flag-comment.env');
+        $dotenv->load();
+
+        $this->assertEquals($_SERVER['CONFIG_SET'], 'true');
+        $this->assertEquals(getenv('CONFIG_SET'), 'true');
+        $this->assertTrue(!isset($_ENV['CONFIG_SET']));
+    }
+
+    /**
+     * @expectedException \Dotenv\Exception\InvalidFileException
+     * @expectedExceptionMessage PHPDOTENV_ flags must appear before any environment variables are set
+     */
+    public function testDotenvFailsWhenConfigFlagOutOfOrder()
+    {
+        $dotenv = new Dotenv(dirname(__DIR__).'/fixtures/env-wrong', 'flag-wrong.env');
+        $dotenv->load();
+    }
 }
diff --git a/tests/fixtures/env-wrong/flag-wrong.env b/tests/fixtures/env-wrong/flag-wrong.env
@@ -0,0 +1,8 @@
+FOO=bar
+BAR=baz
+SPACED="with spaces"
+
+NULL=
+PHPDOTENV_NO_SET_ENV
+
+CONFIG_SET=true
diff --git a/tests/fixtures/env/flag-comment.env b/tests/fixtures/env/flag-comment.env
@@ -0,0 +1,8 @@
+PHPDOTENV_NO_SET_ENV # Comment
+FOO=bar
+BAR=baz
+SPACED="with spaces"
+
+NULL=
+
+CONFIG_SET=true
diff --git a/tests/fixtures/env/flag.env b/tests/fixtures/env/flag.env
@@ -0,0 +1,8 @@
+PHPDOTENV_NO_SET_ENV
+FOO=bar
+BAR=baz
+SPACED="with spaces"
+
+NULL=
+
+CONFIG_SET=true