diff --git a/README.md b/README.md
index 5afbc16..e4b2618 100755
--- a/README.md
+++ b/README.md
@@ -113,19 +113,19 @@ Install required packages :
 * For Centos 7, RHEL 7 and Fedora :
 ```bash
 #For PostgreSQL
-sudo yum -y --nogpgcheck install httpd php postgresql-server postgresql php-ldap php-pdo php-pgsql git
+sudo yum -y --nogpgcheck install httpd php postgresql-server postgresql php-ldap php-pdo php-xml php-pgsql git
 
 #For MySQL
-sudo yum -y --nogpgcheck install httpd php mariadb-server mariadb php-ldap php-pdo php-mysql git
+sudo yum -y --nogpgcheck install httpd php mariadb-server mariadb php-ldap php-pdo php-xml php-mysql git
 ```
 
 * For Debian, ubuntu, Mint :
 ```bash
 #For PostgreSQL
-sudo apt-get -y install httpd php postgresql-server postgresql php-ldap php-pdo php-pgsql git
+sudo apt-get -y install httpd php postgresql-server postgresql php-ldap php-pdo php-dom php-pgsql git
 
 #For MySQL
-sudo apt-get -y install httpd php mariadb-server mariadb php-ldap php-pdo php-mysql git
+sudo apt-get -y install httpd php mariadb-server mariadb php-ldap php-pdo php-dom php-mysql git
 ```
 
 Setup your SQL server with the following command :
diff --git a/oauth/authorize.php b/oauth/authorize.php
index 6de485c..28ca1d5 100644
--- a/oauth/authorize.php
+++ b/oauth/authorize.php
@@ -14,7 +14,7 @@ $request = OAuth2\Request::createFromGlobals();
 $response = new OAuth2\Response();
 
 // If user has clicked on "not me" link, disconnect him by cleaning PHP SESSION variables.
-if ($_POST['disconnect']) {
+if (isset($_POST['disconnect'])) {
     $_SESSION=array();
 }