The curl_init() function returns a Curl instance for us to use in later functions, and you should always store it for later. It has just one optional parameter: if you pass a string into curl_init(), it will automatically use that string as the URL to work with. In the script below, we use curl_setopt() to do that for clarity, but it is all the same
curl_setopt() takes three parameters, which are the Curl instance to use, a constant value for the setting you want to change, and the value you want to use for that setting. There are a huge number of constants you can use for settings, and many of these are listed shortly. In the example we use CURLOPT_URL, which is used to set the URL for Curl to work with, and so the working URL is set to the third parameter
Calling curl_exec() means, "We're finished setting our options, go ahead and do it", and you need to pass precisely one parameter: the Curl resource to use. The return value of curl_exec() is true/false by default
The final function, curl_close(), takes a Curl resource as its only parameter, closes the Curl session, then frees up the associated memory
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, "http://localhost/posttest.php");
curl_setopt($curl, CURLOPT_POST, 1);
curl_setopt($curl, CURLOPT_POSTFIELDS, "Hello=World&Foo=Bar&Baz=Wombat");
curl_exec ($curl);
curl_close ($curl);