500 error when passing variables to function - php

Question

I have the below function in my WordPress functions file, and if I run it as below without the two parameters it works fine, but when I pass the parameters the error handler in the jQuery returns status 500.
If I don't pass the parameters to the PHP function I get status 200 from jQuery, but it's coming from the error handler, and not from the success handler. Why so?
function subscribe_funk(){//$payment_method, $customer_handle){
return "This is a test";
die();
}
It gets called from this ajax:
function subscribe(data) {
jQuery.ajax({
url: PT_Ajax.ajaxurl,
type: "POST",
data: {'action': 'subscribe_funk', 'payment_method': data.payment_method, 'customer_handle': data.customer},
cache: false,
dataType: 'json',
beforeSend: function(){
console.log('Before send subscribe');
},
complete: function(){
},
success: function (response) {
console.log('Message from success handler: ');
console.log(response);
},
error: function(xhr, status, error){
console.log("Message from error handler:")
var errorMessage = xhr.status + ': ' + xhr.statusText
console.log(errorMessage);
}
});
}

Answer 1

Your function expects 2 parameters, however WP/ajax is not passing them directly.
You need to fetch them from $_POST array yourself:
function subscribe_funk(){
$payment_method = $_POST['payment_method'];
$customer_handle = $_POST['customer_handle'];
return "This is a test";
die();
}
Also, you may want to sanitize the post data with sanitize_text_field() or similar function.
Here is a relevant thread in WP StackExchange: how to pass parameters from jQuery ajax to a PHP function