button with function that calling php script

hello, i need to set a button and on click i need to calling a php script.

I tried with ajax but does not work .

what i tried is something like this :

$.ajax({
type: "POST",
url: 'xxx.php',
data: {one:string},
success: function (response) {//response is value returned from php (for your example it's "bye bye"
alert(response);
}
});

any ideas??