Remote form submission via PHP Curl

$user_agent = 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1) Gecko/20061010 Firefox/2.0';
$headers = array (
    'HTTP_ACCEPT' => 'application/x-shockwave-flash,text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5', 
    'HTTP_ACCEPT_LANGUAGE' => 'en-us,en;q=0.5',
    'HTTP_ACCEPT_CHARSET' => 'ISO-8859-1,utf-8;q=0.7,*;q=0.7',
    'HTTP_KEEP_ALIVE' => '300',
    'HTTP_CONNECTION' => 'keep-alive'
    );
    
    

function read_header($ch, $string)
{
   global $location; #keep track of location/redirects
   global $cookiearr; #store cookies here
   global $ch;
       # ^overrides the function param $ch  this is okay because 
       # we need to update the global $ch with new cookies
  
   $length = strlen($string);
   if(!strncmp($string, "Location:", 9)) #keep track of last redirect
   { $location = trim(substr($string, 9, -1)); }
   
   if(!strncmp($string, "Set-Cookie:", 11)) #get the cookie
   { 
     $cookiestr = trim(substr($string, 11, -1));
     $cookie = explode(';', $cookiestr);
     $cookie = explode('=', $cookie[0]);
     $cookiename = trim(array_shift($cookie));
     $cookiearr[$cookiename] = trim(implode('=', $cookie));
   }
   $cookie = "";
   if(trim($string) == "") #execute only at end of header
   {  
     foreach ($cookiearr as $key=>$value) { $cookie .= "$key=$value; "; }
     curl_setopt($ch, CURLOPT_COOKIE, $cookie);
   }

   return $length;
}



$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADERFUNCTION, 'read_header');  # take their cookie and love it!
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
curl_setopt($ch, CURLOPT_AUTOREFERER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
curl_setopt($ch, CURLOPT_REFERER, $url_base);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_URL, $url_login);

$string = curl_exec($ch);