PHP code example:

$ch = curl_init();
$value = '';
curl_setopt($ch, CURLOPT_URL, $value);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

curl_setopt( $ch, CURLOPT_POSTFIELDS, 'type=basic&user=YOUR_API_KEY&text='.$content);  
$xml = curl_exec($ch);

Test Post form

The following is a simple form that posts 2 values : the fist is the type = basic and the second is input box content:

<form action="keyrest.php" method="post" enctype="multipart/form-data" name="form">
<textarea name="text">Cut and paste an article</textarea>
<input name= "type" type="hidden" value="basic" >
<input name= "user" type="hidden" value="YOUR_API_KEY" >
<input name="submit" type="submit" value="Find Keywords" />

Try it :