gistfile1.js

function getFile() {
    var postData = "foo=bar&this=that";
    var request = YAHOO.util.Connect.asyncRequest('POST', 'script.php', getFileCallback, postData);
}

getFileCallback = {
    success: function(o) {
        panel.setBody(o.responseText);
    },
    failure: function(o) {
        alert("Failed");
    }
}