Why do you want to make a round trip to the server just to copy the button value to a label on the same page, can't you just do it with JavaScript or jQuery?
However,, if you insist:
This
success: function(data){
alert(data);
is missing a closing
}
I wonder why this
$(".123").toggle();
for?
You did not show your html code, make sure you button look similar to this:
<button class="1234" value="The button value that you want">click me</button>
In the test.php,
<?php
if (isset($_REQUEST["C_ID"]))
echo $_REQUEST["C_ID"];
?>
Last but not least, you can achieve the same objective using just jQuery:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$(".1234").click(function() {
$('label').html($(this).val());
})
})
</script>
</head>
<body>
<label></label>
<button class="1234" value="Hello, Button!">click me</button>
</body>
</html>