$connection = ssh2_connect($SFTP_SERVER, 22);
ssh2_auth_password($connection,$SFTP_USERNAME,$SFTP_PASSWORD);
$sftp = ssh2_sftp($connection);
Fatal error: Call to undefined function ssh2_connect() in /var/www/html/beta/0sftp.php on line 33
my system is CentOS 6.4 all the required extensions is installed but I don't know how to verify.