do it do it like this ?
//IF THE FORM WAS SUBMITTED
if(isset($_POST['submit'])) {
//GET USER-SUGGESTED PROXIES
$proxies = trim($_POST['proxies']);
var_dump($proxies); //<-- this line just shows that a value was passed; it isn't needed for your final code
//...do whatever you need to do with the proxies here...
$ch = curl_init('https://www.website.com');
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_PROXY, $proxy);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER,0);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT,15);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($ch, CURLOPT_HTTP_VERSION,'CURL_HTTP_VERSION_1_1' );
curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1);
curl_setopt($ch, CURLOPT_ENCODING , "gzip,deflate");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
curl_setopt($ch, CURLOPT_PROXY, $proxy);
curl_setopt($ch, CURLOPT_PROXY, $proxy_ip);
curl_setopt($ch, CURLOPT_REFERER, $refer);
curl_setopt($ch, CURLOPT_USERAGENT,$agents[array_rand($agents)]);
curl_setopt($ch, CURLOPT_PROXY,$proxies[array_rand($proxies)]);
curl_setopt($ch, CURLOPT_COOKIEFILE, dirname(__FILE__).'/cookie.txt');
curl_setopt($ch, CURLOPT_COOKIEJAR, dirname(__FILE__).'/cookie.txt');
}