diff --git a/src/webim/button.php b/src/webim/button.php
index 5d272253..46e7a071 100644
--- a/src/webim/button.php
+++ b/src/webim/button.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('libs/common.php');
-require('libs/operator.php');
+require_once('libs/common.php');
+require_once('libs/operator.php');
 
 $image = verifyparam("image","/^\w+$/", "webim");
 $lang = verifyparam("lang", "/^[\w-]{2,5}$/", "");
diff --git a/src/webim/client.php b/src/webim/client.php
index 35f59615..26f8b141 100644
--- a/src/webim/client.php
+++ b/src/webim/client.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('libs/common.php');
-require('libs/chat.php');
-require('libs/operator.php');
+require_once('libs/common.php');
+require_once('libs/chat.php');
+require_once('libs/operator.php');
 
 if( !isset($_GET['token']) || !isset($_GET['thread']) ) {
 
diff --git a/src/webim/install/dbperform.php b/src/webim/install/dbperform.php
index c41c510a..5e4eff6b 100644
--- a/src/webim/install/dbperform.php
+++ b/src/webim/install/dbperform.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
-require('dbinfo.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
+require_once('dbinfo.php');
 
 function runsql($query,$link) {
 	mysql_query($query,$link)
diff --git a/src/webim/install/index.php b/src/webim/install/index.php
index d02af585..8c4c883c 100644
--- a/src/webim/install/index.php
+++ b/src/webim/install/index.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('dbinfo.php');
+require_once('../libs/common.php');
+require_once('dbinfo.php');
 
 $page = array(
 	'version' => $version,
diff --git a/src/webim/leavemessage.php b/src/webim/leavemessage.php
index ba7ad5f9..bcff0d24 100644
--- a/src/webim/leavemessage.php
+++ b/src/webim/leavemessage.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('libs/common.php');
-require('libs/chat.php');
+require_once('libs/common.php');
+require_once('libs/chat.php');
 
 $errors = array();
 $page = array();
diff --git a/src/webim/libs/common.php b/src/webim/libs/common.php
index 91e596b2..9e782f40 100644
--- a/src/webim/libs/common.php
+++ b/src/webim/libs/common.php
@@ -14,8 +14,8 @@
 
 session_start();
 
-require(dirname(__FILE__).'/converter.php');
-require(dirname(__FILE__).'/config.php');
+require_once(dirname(__FILE__).'/converter.php');
+require_once(dirname(__FILE__).'/config.php');
 
 $version = 'v1.0.9';
 
diff --git a/src/webim/mail.php b/src/webim/mail.php
index a00ccb1b..b9a06bec 100644
--- a/src/webim/mail.php
+++ b/src/webim/mail.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('libs/common.php');
-require('libs/chat.php');
+require_once('libs/common.php');
+require_once('libs/chat.php');
 
 $errors = array();
 $page = array();
diff --git a/src/webim/operator/agent.php b/src/webim/operator/agent.php
index 0f98d29c..4fb82857 100644
--- a/src/webim/operator/agent.php
+++ b/src/webim/operator/agent.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/chat.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/chat.php');
+require_once('../libs/operator.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/getcode.php b/src/webim/operator/getcode.php
index c4b08b92..6d43e238 100644
--- a/src/webim/operator/getcode.php
+++ b/src/webim/operator/getcode.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/history.php b/src/webim/operator/history.php
index bc14c382..78a24145 100644
--- a/src/webim/operator/history.php
+++ b/src/webim/operator/history.php
@@ -12,10 +12,10 @@
  *    Pavel Petroshenko - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
-require('../libs/chat.php');
-require('../libs/pagination.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
+require_once('../libs/chat.php');
+require_once('../libs/pagination.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/index.php b/src/webim/operator/index.php
index 17ce0289..ce9fc8e9 100644
--- a/src/webim/operator/index.php
+++ b/src/webim/operator/index.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/login.php b/src/webim/operator/login.php
index 4cd78476..97ca7fb3 100644
--- a/src/webim/operator/login.php
+++ b/src/webim/operator/login.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 $errors = array();
 if( isset($_POST['login']) && isset($_POST['password']) ) {
diff --git a/src/webim/operator/logout.php b/src/webim/operator/logout.php
index 339569df..d1d4b655 100644
--- a/src/webim/operator/logout.php
+++ b/src/webim/operator/logout.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 logout_operator();
 
diff --git a/src/webim/operator/operator.php b/src/webim/operator/operator.php
index f0373c38..14e3b673 100644
--- a/src/webim/operator/operator.php
+++ b/src/webim/operator/operator.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/operators.php b/src/webim/operator/operators.php
index bebe6453..e44d69ba 100644
--- a/src/webim/operator/operators.php
+++ b/src/webim/operator/operators.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/threadprocessor.php b/src/webim/operator/threadprocessor.php
index f1583658..897f855d 100644
--- a/src/webim/operator/threadprocessor.php
+++ b/src/webim/operator/threadprocessor.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
-require('../libs/chat.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
+require_once('../libs/chat.php');
 
 $operator = check_login();
 
diff --git a/src/webim/operator/update.php b/src/webim/operator/update.php
index ee5cec36..f0ca98b9 100644
--- a/src/webim/operator/update.php
+++ b/src/webim/operator/update.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/chat.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/chat.php');
+require_once('../libs/operator.php');
 
 $operator = get_logged_in();
 if( !$operator ) {
diff --git a/src/webim/operator/users.php b/src/webim/operator/users.php
index 67674af8..3cf94650 100644
--- a/src/webim/operator/users.php
+++ b/src/webim/operator/users.php
@@ -12,8 +12,8 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('../libs/common.php');
-require('../libs/operator.php');
+require_once('../libs/common.php');
+require_once('../libs/operator.php');
 
 
 $operator = check_login();
diff --git a/src/webim/thread.php b/src/webim/thread.php
index fd7917fa..2337fbaf 100644
--- a/src/webim/thread.php
+++ b/src/webim/thread.php
@@ -12,9 +12,9 @@
  *    Evgeny Gryaznov - initial API and implementation
  */
 
-require('libs/common.php');
-require('libs/chat.php');
-require('libs/operator.php');
+require_once('libs/common.php');
+require_once('libs/chat.php');
+require_once('libs/operator.php');
 
 $act = verifyparam( "act", "/^(refresh|post|rename|close|ping".")$/");
 $token = verifyparam( "token", "/^\d{1,9}$/");