diff --git a/core/includes/install.inc b/core/includes/install.inc
index 74d8e39..49c6c64 100644
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -162,6 +162,44 @@ function drupal_get_database_types() {
 }
 
 /**
+ * Flushes a PHP file from any active opcode cache.
+ *
+ * If it is not possible to flush an individual file, the whole cache will be
+ * flushed.
+ *
+ * @param string $filepath
+ *   Filepath of PHP file to be flushed.
+ */
+function drupal_clear_opcode_cache($filepath) {
+  // Do nothing if the file does not exist or it stat fails.
+  clearstatcache(TRUE, $filepath);
+  if (!file_exists($filepath) || !@stat($filepath)) {
+    return;
+  }
+
+  try {
+    if (function_exists('opcache_invalidate')) {
+      opcache_invalidate($filepath);
+    }
+    if (function_exists('apc_delete_file')) {
+      apc_delete_file($filepath);
+    }
+    if (function_exists('wincache_refresh_if_changed')) {
+      wincache_refresh_if_changed(array($filepath));
+    }
+    if (function_exists('xcache_clear_cache')) {
+      xcache_clear_cache(XC_TYPE_PHP);
+    }
+    if (function_exists('eaccelerator_clear')) {
+      eaccelerator_clear();
+    }
+  }
+  catch (Exception $e) {
+    throw new Exception(t('Failed to clear the opcode cache for %settings. For the duration of the installation it is recommended to either disable the opcode cache, or reconfigure it to allow code changes to be seen immediately.', array('%settings' => $settings_file)));
+  }
+}
+
+/**
  * Replaces values in settings.php with values in the submitted array.
  *
  * This function replaces values in place if possible, even for
@@ -194,6 +232,7 @@ function drupal_rewrite_settings($settings = array(), $settings_file = NULL) {
   if (!isset($settings_file)) {
     $settings_file = conf_path(FALSE) . '/settings.php';
   }
+  $filepath = DRUPAL_ROOT . '/' . $settings_file;
   // Build list of setting names and insert the values into the global namespace.
   $variable_names = array();
   $settings_settings = array();
@@ -206,7 +245,7 @@ function drupal_rewrite_settings($settings = array(), $settings_file = NULL) {
     }
     $variable_names['$'. $setting] = $setting;
   }
-  $contents = file_get_contents(DRUPAL_ROOT . '/' . $settings_file);
+  $contents = file_get_contents($filepath);
   if ($contents !== FALSE) {
     // Step through each token in settings.php and replace any variables that
     // are in the passed-in array.
@@ -307,7 +346,7 @@ function drupal_rewrite_settings($settings = array(), $settings_file = NULL) {
     }
 
     // Write the new settings file.
-    if (file_put_contents(DRUPAL_ROOT . '/' . $settings_file, $buffer) === FALSE) {
+    if (file_put_contents($filepath, $buffer) === FALSE) {
       throw new Exception(t('Failed to modify %settings. Verify the file permissions.', array('%settings' => $settings_file)));
     }
     else {
@@ -322,6 +361,8 @@ function drupal_rewrite_settings($settings = array(), $settings_file = NULL) {
   else {
     throw new Exception(t('Failed to open %settings. Verify the file permissions.', array('%settings' => $settings_file)));
   }
+  // Remove settings.php from any active opcode cache.
+  drupal_clear_opcode_cache($filepath);
 }
 
 /**