#547846 by David_Rothstein: Fixed a missing reference operator that caused Drupal installation to fail on PHP 5.3.

includes/form.inc

@@ -442,6 +442,9 @@ function drupal_retrieve_form($form_id, &$form_state) {
     }
   }
 
+ // We need to pass $form_state by reference in order for forms to modify it,
+ // since call_user_func_array() requires that referenced variables be passed
+ // explicitly.
   $args = array_merge(array(&$form_state), $args);
 
   // If $callback was returned by a hook_forms() implementation, call it.

install.php

@@ -386,7 +386,10 @@ function install_run_task($task, &$install_state) {
       // redirect, since the installer handles its own redirection only after
       // marking the form submission task complete.
       $form_state = array(
-        'args' => array($install_state),
+        // We need to pass $install_state by reference in order for forms to
+        // modify it, since the form API will use it in call_user_func_array(),
+        // which requires that referenced variables be passed explicitly.
+        'args' => array(&$install_state),
         'no_redirect' => TRUE,
       );
       $form = drupal_build_form($function, $form_state);