Ai giúp mình kiểm tra đoạn code này xem sai ở đâu với

Khi mình up code lên host thì báo:
A PHP Error was encountered
Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at /home/cameee23/public_html/application/config/config.php:1)

Filename: libraries/Session.php

Line Number: 672

Đoạn code :
{
if (is_null($cookie_data))
{
$cookie_data = $this->userdata;
}

// Serialize the userdata for the cookie
$cookie_data = $this->_serialize($cookie_data);

if ($this->sess_encrypt_cookie == TRUE)
{
$cookie_data = $this->CI->encrypt->encode($cookie_data);
}
else
{
// if encryption is not used, we provide an md5 hash to prevent userside tampering
$cookie_data = $cookie_data.md5($cookie_data.$this->encryption_key);
}

$expire = ($this->sess_expire_on_close === TRUE) ? 0 : $this->sess_expiration + time();

// Set the cookie
setcookie(
$this->sess_cookie_name,
$cookie_data,
$expire,
$this->cookie_path,
$this->cookie_domain,
$this->cookie_secure
);
Báo lỗi dòng 672 ( thông tin code dòng 672 : ); )A PHP Error was encountered
Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at /home/cameee23/public_html/application/config/config.php:1)

Filename: libraries/Session.php

Line Number: 672