diff --git a/INSTALL.txt b/INSTALL.txt
index 1e80540..4154324 100644
--- a/INSTALL.txt
+++ b/INSTALL.txt
@@ -21,13 +21,12 @@ are created automatically.
 REQUIREMENTS
 ------------
 
-Drupal requires a web server, PHP4 (4.3.5 or greater) or PHP5 (through 5.2.x
-only; 5.3.x and later versions are not supported) (http://php.net/) and either
-MySQL (http://www.mysql.com/) or PostgreSQL (http://www.postgresql.org/). The
-Apache web server and MySQL database are recommended; other web server and
-database combinations such as IIS and PostgreSQL have been tested to a lesser
-extent. When using MySQL, version 4.1 or greater is recommended to assure you
-can safely transfer the database.
+Drupal requires a web server, PHP4 (4.3.5 or greater) or PHP5 (http://php.net/)
+and either MySQL (http://www.mysql.com/) or PostgreSQL
+(http://www.postgresql.org/). The Apache web server and MySQL database are
+recommended; other web server and database combinations such as IIS and
+PostgreSQL have been tested to a lesser extent. When using MySQL, version 4.1 or
+greater is recommended to assure you can safely transfer the database.
 
 For more detailed information about Drupal requirements, see "Requirements"
 (http://drupal.org/requirements) in the Drupal Handbook.
diff --git a/includes/common.inc b/includes/common.inc
index d1bcb2f..75ffc93 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -24,6 +24,13 @@ define('SAVED_UPDATED', 2);
 define('SAVED_DELETED', 3);
 
 /**
+ * Create E_DEPRECATED constant for older PHP versions (<5.3).
+ */
+if (!defined('E_DEPRECATED')) {
+  define('E_DEPRECATED', 8192);
+}
+
+/**
  * Set content for a specified region.
  *
  * @param $region
@@ -588,7 +595,7 @@ function error_handler($errno, $message, $filename, $line) {
     return;
   }
 
-  if ($errno & (E_ALL ^ E_NOTICE)) {
+  if ($errno & (E_ALL & ~E_NOTICE & ~E_DEPRECATED)) {
     $types = array(1 => 'error', 2 => 'warning', 4 => 'parse error', 8 => 'notice', 16 => 'core error', 32 => 'core warning', 64 => 'compile error', 128 => 'compile warning', 256 => 'user error', 512 => 'user warning', 1024 => 'user notice', 2048 => 'strict warning', 4096 => 'recoverable fatal error');
     $entry = $types[$errno] .': '. $message .' in '. $filename .' on line '. $line .'.';
 
diff --git a/includes/file.inc b/includes/file.inc
index ee65d62..6ef5fae 100644
--- a/includes/file.inc
+++ b/includes/file.inc
@@ -642,7 +642,7 @@ function file_scan_directory($dir, $mask, $nomask = array('.', '..', 'CVS'), $ca
         if (is_dir("$dir/$file") && $recurse) {
           $files = array_merge($files, file_scan_directory("$dir/$file", $mask, $nomask, $callback, $recurse, $key, $min_depth, $depth + 1));
         }
-        elseif ($depth >= $min_depth && ereg($mask, $file)) {
+        elseif ($depth >= $min_depth && @ereg($mask, $file)) {
           $filename = "$dir/$file";
           $basename = basename($file);
           $name = substr($basename, 0, strrpos($basename, '.'));
diff --git a/includes/module.inc b/includes/module.inc
index 34dcc43..feca604 100644
--- a/includes/module.inc
+++ b/includes/module.inc
@@ -378,8 +378,9 @@ function module_implements($hook, $sort = FALSE, $refresh = FALSE) {
  */
 function module_invoke() {
   $args = func_get_args();
-  $module = array_shift($args);
-  $hook = array_shift($args);
+  $module = $args[0];
+  $hook = $args[1];
+  unset($args[0], $args[1]);
   $function = $module .'_'. $hook;
   if (module_hook($module, $hook)) {
     return call_user_func_array($function, $args);
diff --git a/includes/theme.inc b/includes/theme.inc
index 38ec6e6..ea2a4ff 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -167,6 +167,10 @@ function theme() {
     $functions[$function] = theme_get_function($function);
   }
   if ($functions[$function]) {
+    // Force the arguments to pass through by reference.
+    foreach($args as $i => &$arg){
+      $args[$i] = &$arg;
+    }
     $output = call_user_func_array($functions[$function], $args);
     // Add final markup to the full page.
     if ($function == 'page' || $function == 'book_export_html') {
diff --git a/includes/unicode.inc b/includes/unicode.inc
index 71b40af..92ff1f8 100644
--- a/includes/unicode.inc
+++ b/includes/unicode.inc
@@ -134,7 +134,7 @@ function drupal_xml_parser_create(&$data) {
   }
 
   // Check for an encoding declaration in the XML prolog if no BOM was found.
-  if (!$bom && ereg('^<\?xml[^>]+encoding="([^"]+)"', $data, $match)) {
+  if (!$bom && @ereg('^<\?xml[^>]+encoding="([^"]+)"', $data, $match)) {
     $encoding = $match[1];
   }
 
diff --git a/modules/block/block.module b/modules/block/block.module
index 24a8351..24fe67c 100644
--- a/modules/block/block.module
+++ b/modules/block/block.module
@@ -588,7 +588,7 @@ function block_box_save($edit, $delta = NULL) {
  * Allow users to decide which custom blocks to display when they visit
  * the site.
  */
-function block_user($type, $edit, &$account, $category = NULL) {
+function block_user($type, $edit, $account, $category = NULL) {
   switch ($type) {
     case 'form':
       if ($category == 'account') {
diff --git a/modules/comment/comment.info b/modules/comment/comment.info
index 63139a1..3fe8919 100644
--- a/modules/comment/comment.info
+++ b/modules/comment/comment.info
@@ -1,4 +1,4 @@
 name = Comment
-description = Allows users to comment on and discuss published content.
+description = "Allows users to comment on and discuss published content."
 package = Core - optional
 version = VERSION
diff --git a/modules/contact/contact.info b/modules/contact/contact.info
index 08cc5ab..e04d289 100644
--- a/modules/contact/contact.info
+++ b/modules/contact/contact.info
@@ -1,4 +1,4 @@
 name = Contact
-description = Enables the use of both personal and site-wide contact forms.
+description = "Enables the use of both personal and site-wide contact forms."
 package = Core - optional
 version = VERSION
diff --git a/modules/drupal/drupal.info b/modules/drupal/drupal.info
index b5dfda6..0f59027 100644
--- a/modules/drupal/drupal.info
+++ b/modules/drupal/drupal.info
@@ -1,4 +1,4 @@
 name = Drupal
-description = Lets you register your site with a central server and improve ranking of Drupal projects by posting information on your installed modules and themes; also enables users to log in using a Drupal ID.
+description = "Lets you register your site with a central server and improve ranking of Drupal projects by posting information on your installed modules and themes; also enables users to log in using a Drupal ID."
 package = Core - optional
 version = VERSION
diff --git a/modules/node/node.info b/modules/node/node.info
index 0f6a279..b01c5e3 100644
--- a/modules/node/node.info
+++ b/modules/node/node.info
@@ -1,4 +1,4 @@
 name = Node
-description = Allows content to be submitted to the site and displayed on pages.
+description = "Allows content to be submitted to the site and displayed on pages."
 package = Core - required
 version = VERSION
diff --git a/modules/poll/poll.info b/modules/poll/poll.info
index c446051..466985e 100644
--- a/modules/poll/poll.info
+++ b/modules/poll/poll.info
@@ -1,4 +1,4 @@
 name = Poll
-description = Allows your site to capture votes on different topics in the form of multiple choice questions.
+description = "Allows your site to capture votes on different topics in the form of multiple choice questions."
 package = Core - optional
 version = VERSION
diff --git a/modules/system/system.module b/modules/system/system.module
index 96b9b05..d3f97b9 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -324,7 +324,7 @@ function system_menu($may_cache) {
  *
  * Allows users to individually set their theme and time zone.
  */
-function system_user($type, $edit, &$user, $category = NULL) {
+function system_user($type, $edit, $user, $category = NULL) {
   if ($type == 'form' && $category == 'account') {
     $form['theme_select'] = system_theme_select_form(t('Selecting a different theme will change the look and feel of the site.'), $edit['theme'], 2);
 
@@ -1863,7 +1863,7 @@ function _system_sort_requirements($a, $b) {
 /**
  * Theme status report
  */
-function theme_status_report(&$requirements) {
+function theme_status_report($requirements) {
   $i = 0;
   $output = '<table class="system-status-report">';
   foreach ($requirements as $requirement) {
diff --git a/modules/upload/upload.module b/modules/upload/upload.module
index 883b326..45575f3 100644
--- a/modules/upload/upload.module
+++ b/modules/upload/upload.module
@@ -814,7 +814,7 @@ function _upload_form($node) {
 /**
  * Theme the attachments list.
  */
-function theme_upload_form_current(&$form) {
+function theme_upload_form_current($form) {
   $header = array(t('Delete'), t('List'), t('Description'), t('Size'));
 
   foreach (element_children($form) as $key) {
diff --git a/modules/user/user.module b/modules/user/user.module
index 17354c4..a4ec5e1 100644
--- a/modules/user/user.module
+++ b/modules/user/user.module
@@ -259,7 +259,7 @@ function user_validate_name($name) {
   if (substr($name, 0, 1) == ' ') return t('The username cannot begin with a space.');
   if (substr($name, -1) == ' ') return t('The username cannot end with a space.');
   if (strpos($name, '  ') !== FALSE) return t('The username cannot contain multiple spaces in a row.');
-  if (ereg("[^\x80-\xF7 [:alnum:]@_.-]", $name)) return t('The username contains an illegal character.');
+  if (@ereg("[^\x80-\xF7 [:alnum:]@_.-]", $name)) return t('The username contains an illegal character.');
   if (preg_match('/[\x{80}-\x{A0}'.          // Non-printable ISO-8859-1 + NBSP
                    '\x{AD}'.                 // Soft-hyphen
                    '\x{2000}-\x{200F}'.      // Various space characters
@@ -463,7 +463,7 @@ function user_search($op = 'search', $keys = NULL) {
 /**
  * Implementation of hook_user().
  */
-function user_user($type, &$edit, &$user, $category = NULL) {
+function user_user($type, &$edit, $user, $category = NULL) {
   if ($type == 'view') {
     $items['history'] = array('title' => t('Member for'),
       'value' => format_interval(time() - $user->created),
@@ -1042,7 +1042,9 @@ function user_logout() {
 
   // Destroy the current session:
   session_destroy();
-  module_invoke_all('user', 'logout', NULL, $user);
+  // Only variables can be passed by reference workaround.
+  $null = NULL;
+  user_module_invoke('logout', $null, $user);
 
   // Load the anonymous user
   $user = drupal_anonymous_user();
@@ -1504,7 +1506,7 @@ function user_delete($edit, $uid) {
   $array = array('%name' => $account->name, '%email' => '<'. $account->mail .'>');
   watchdog('user', t('Deleted user: %name %email.', $array), WATCHDOG_NOTICE);
   drupal_set_message(t('%name has been deleted.', $array));
-  module_invoke_all('user', 'delete', $edit, $account);
+  user_module_invoke('delete', $edit, $account);
 }
 
 function user_edit_validate($form_id, $form_values) {
@@ -1544,8 +1546,11 @@ function user_view($uid = 0) {
   }
   // Retrieve and merge all profile fields:
   $fields = array();
+  $null = NULL;
   foreach (module_list() as $module) {
-    if ($data = module_invoke($module, 'user', 'view', '', $account)) {
+    $function = $module .'_user';
+    // $null and $account need to be passed by reference.
+    if (function_exists($function) && ($data = $function('view', $null, $account, ''))) {
       foreach ($data as $category => $items) {
         foreach ($items as $key => $item) {
           $item['class'] = "$module-". $item['class'];
@@ -2455,8 +2460,12 @@ function user_help_page() {
 function _user_categories($account) {
   $categories = array();
 
+  // Only variables can be passed by reference workaround.
+  $null = NULL;
   foreach (module_list() as $module) {
-    if ($data = module_invoke($module, 'user', 'categories', NULL, $account, '')) {
+    $function = $module .'_user';
+    // $null and $account need to be passed by reference.
+    if (function_exists($function) && ($data = $function('categories', $null, $account, ''))) {
       $categories = array_merge($data, $categories);
     }
   }
@@ -2478,7 +2487,9 @@ function _user_sort($a, $b) {
 function _user_forms(&$edit, $account, $category, $hook = 'form') {
   $groups = array();
   foreach (module_list() as $module) {
-    if ($data = module_invoke($module, 'user', $hook, $edit, $account, $category)) {
+    $function = $module .'_user';
+    // $edit and $account need to be passed by reference.
+    if (function_exists($function) && ($data = $function($hook, $edit, $account, $category))) {
       $groups = array_merge_recursive($data, $groups);
     }
   }
diff --git a/modules/watchdog/watchdog.module b/modules/watchdog/watchdog.module
index abf1307..6c20844 100644
--- a/modules/watchdog/watchdog.module
+++ b/modules/watchdog/watchdog.module
@@ -72,7 +72,7 @@ function watchdog_cron() {
 /**
  * Implementation of hook_user().
  */
-function watchdog_user($op, &$edit, &$user) {
+function watchdog_user($op, &$edit, $user) {
   if ($op == 'delete') {
     db_query('UPDATE {watchdog} SET uid = 0 WHERE uid = %d', $user->uid);
   }