redirect form request for options.php – edit data first

hi

i am writing a plugin for wordpress witch stores data in option fields.
so i have a nice form that submits to options.php, works fine, no problem at all.

but i need to check and change some data first, before it is saved.
for example, i have a email field split in to parts, one before the ‘@’ and one after it, and i need php to make it one field and save it.
or make a JSON string of something… or maybe make some thing all lowercase…

so my question is, how do i save option fields without js and forms, pure php.
can i access them like set_option_field() or something?
i tried this with curl:

<?php
ini_set('display_errors', 'On');
error_reporting(E_ALL);

if($_SERVER['REQUEST_METHOD'] === "POST") {
	$url = "https://localhost:8888/michael/wordpress/wp-admin/options.php";
	//$url = "https://localhost:8888/michael/wordpress/wp-content/plugins/programmering/test.php";
	$ch = curl_init();

	// set the target url
	curl_setopt($ch, CURLOPT_URL,$url);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	// howmany parameter to post
	curl_setopt($ch, CURLOPT_POST, count($_POST));

	$fields = "";
	foreach($_POST as $key => $value) {
		$fields .= $key ."=". $value ."&";
	}
	//echo $fields;
	//echo "hoi";

	curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

	$result = curl_exec($ch);
	curl_close($ch);
	echo $result;
} else die("hacking atempt!");
?>

but it does not work…