This function not exists for mysqli db extension. For Persistent Connections can use p: prefix by hostname at php 5.3.

fix:

function mysqli_pconnect($host, $username, $password, $new_link = false, $port = 0)
{
    if($port)
    {
        mysqli_connect("p:".$host, $username, $password, $new_link, $port);
    }
    else
    {
        mysqli_connect("p:".$host, $username, $password, $new_link);
    }
}

for more infomation:http://us1.php.net/manual/zh/mysqli.construct.php