What options we set here?
First we set the connection timeout to 30 seconds, so we don’t have our script waiting indefinitely if the remote server fails to respond.
Then we set how cURL will identify itself to the remote server. Some servers will return different content for different browsers (or agents, such as spiders of the search engines), so we want our request to look like it is coming from a popular browser.

CURLOPT_RETURNTRANSFER set to true forces cURL not to display the output of the request, but return it as a string.

Then we set CURLOPT_SSL_VERIFYPEER option to false, so the request will not trigger an error in case of an invalid, expired or not signed SSL certificate.
Finally, we set CURLOPT_FOLLOWLOCATION to 1 to instruct cURL to follow “Location:” redirects found in the headers sent by the remote site.
Now we must prepare the data that we want to post. We can first store this in an array, with the key of an element being the same as the input name of a regular form, and the value being the value that we want to post for that field.

For example, if in a regular form we would have:



we add this to our array like this:
$post_data['firstName'] = ‘Name’;
$post_data['action'] = ‘Register’;
Do the same for every form field.
Data will be posted in the following format:
key1=value1&key2=value2

In order to format the data like this, we are going to create strings for each key-value pair (for example key1=value1), put them in another array ($post_items) then combine them in one string using PHP function implode() .
foreach ( $post_data as $key => $value) {
$post_items[] = $key . ‘=’ . $value;
}
$post_string = implode (’&’, $post_items);
Next, we need to tell cURL which string we want to post. For this, we use the CURLOPT_POSTFIELDS option.

curl_setopt($curl_connection, CURLOPT_POSTFIELDS, $post_string);
Finally, we execute the post, then close the connection.
$result = curl_exec($curl_connection);
curl_close($curl_connection);
By now, the data should have been posted to the remote URL. Go check this, and if it did not work properly, use curl_getinfo() function to see any errors that might have occurred.
print_r(curl_getinfo($curl_connection));
This line displays an array of information regarding the transfer. This must be used before closing the connection with curl_close();
You can also see number and description of the error by outputting curl_errno($curl_connection) and curl_error($curl_connection).
So let’s put everything together. Here is our code:

//create array of data to be posted
$post_data['firstName'] = ‘Name’;
$post_data['action'] = ‘Register’;
//traverse array and prepare data for posting (key1=value1)
foreach ( $post_data as $key => $value) {
$post_items[] = $key . ‘=’ . $value;
}
//create the final string to be posted using implode()
$post_string = implode (’&’, $post_items);
//create cURL connection
$curl_connection = curl_init(’http://www.domainname.com/target_url.php’);
//set options
curl_setopt($curl_connection, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($curl_connection, CURLOPT_USERAGENT, “Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)”);
curl_setopt($curl_connection, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl_connection, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl_connection, CURLOPT_FOLLOWLOCATION, 1);
//set data to be posted
curl_setopt($curl_connection, CURLOPT_POSTFIELDS, $post_string);
//perform our request
$result = curl_exec($curl_connection);
//show information regarding the request
print_r(curl_getinfo($curl_connection));
echo curl_errno($curl_connection) . ‘-’ . curl_error($curl_connection);
//close the connection
curl_close($curl_connection);
?>