Add RemapKeysFilter

Author: josegonzalez

README.markdown

@@ -297,6 +297,7 @@ The following filters are built into php-dotenv.
 - `josegonzalez\Dotenv\Filter\CallableFilter`: Wraps a callable and invokes it upon the environment.
 - `josegonzalez\Dotenv\Filter\LowercaseKeyFilter`: Lowercases all the keys for an environment to a single-depth.
 - `josegonzalez\Dotenv\Filter\NullFilter`: Returns the environment data without any changes.
+- `josegonzalez\Dotenv\Filter\RemapKeysFilter`: Remaps specific keys in a `$config` array to a set of values at a single-depth.
 - `josegonzalez\Dotenv\Filter\UnderscoreArrayFilter`: Expands a flat array to a nested array. For example, `['0_Foo_Bar' => 'Far']` becomes `[['Foo' => ['Bar' => 'Far']]]`.
 - `josegonzalez\Dotenv\Filter\UppercaseFirstKeyFilter`: Uppercases the first letter for all the keys for an environment to a single-depth..
 - `josegonzalez\Dotenv\Filter\UrlParseFilter`: When there is a key with the suffix `_URL`, this filter uses `parse_url` to add extra data to the environment.

src/josegonzalez/Dotenv/Filter/RemapKeysFilter.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace josegonzalez\Dotenv\Filter;
+
+class RemapKeysFilter
+{
+    /**
+     * Remaps specific keys in a $config array to a set of values at a single-depth.
+     *
+     * @param array $environment Array of environment data
+     * @param array $config Array of keys to remap to specific values
+     * @return array
+     */
+    public function __invoke(array $environment, array $config)
+    {
+        foreach ($config as $key => $value) {
+            if (array_key_exists($key, $environment)) {
+                $environment[$value] = $environment[$key];
+                unset($environment[$key]);
+            }
+        }
+        return $environment;
+    }
+}

tests/josegonzalez/Dotenv/LoaderTest.php

@@ -331,6 +331,28 @@ public function testNullFilter()
         ), $this->Loader->toArray());
     }
 
+
+    /**
+     * @covers \josegonzalez\Dotenv\Filter\RemapKeysFilter::__invoke
+     */
+    public function testRemapKeysFilter()
+    {
+        $this->Loader->setFilters(array(
+            'josegonzalez\Dotenv\Filter\RemapKeysFilter' => array(
+                'FOO' => 'QUX'
+            ),
+        ));
+        $this->Loader->setFilepath($this->fixturePath . '.env');
+        $this->Loader->parse();
+        $this->Loader->filter();
+        $this->assertEquals(array(
+            'QUX' => 'bar',
+            'BAR' => 'baz',
+            'SPACED' => 'with spaces',
+            'EQUALS' => 'pgsql:host=localhost;dbname=test',
+        ), $this->Loader->toArray());
+    }
+
     /**
      * @covers \josegonzalez\Dotenv\Filter\UppercaseFirstKeyFilter::__invoke
      */