PHP not echoing back data from form submit - php

Question

My page has an html form to collect email, first name, last name and a checkbox. The form begins with this header:
<form action="echo_test.php" method="post" name='register' id='register'>
I submit the form with this button:
<div class="EMail_Pwd_JoinPage"><button class="btn_joinnow" style="color:rgb(255,255,255);" id="btn_submit" onclick="GetDate(); GetCkBx();">Submit data</button></div>
That calls this jquery function:
<script type="text/javascript">
$("#btn_submit").on("click", function (event) {
event.preventDefault();
form_data = $('form').serialize()
console.log("Okay, I'm starting");
console.log(form_data);
console.log("More Info");
GetDate();
return $.ajax({
type: "POST",
url: "echo_test.php",
data: form_data,
success: function (responseText) {
console.log("Server Reply " + responseText);
},
error: function (error) {
console.log("Okay, I failed" + error);
}
});
});
</script>
It submits to echo_test.php on my server:
<?php
echo 'Hello ' . htmlspecialchars($_POST["firstname"]) . '!';
?>
In the onclick event submit code above it should reply from the server:
success: function (responseText) {
console.log("Server Reply " + responseText);
},
But the Chrome dev console does not show any reply. The other console.log messages above do appear correctly (including the serialized form data).
I asked a similar question back in May, but the situation is different here.
Why doesn't this code echo back from the server?

Answer 1

Idk what does onclick attribute mean,
onclick="GetDate(); GetCkBx();"
So i think just remove onclick attribute. And here new code,
<div class="EMail_Pwd_JoinPage"><button type="submit" class="btn_joinnow" style="color:rgb(255,255,255);" id="btn_submit">Submit data</button></div>
Also update your button action jQuery code,
$("#btn_submit").on("submit",

Answer 2

As per my comment, remove onclick="GetDate(); GetCkBx();" from the button tag and call those two functions in the click event handler you created.
New Button Tag:
<button class="btn_joinnow" style="color:rgb(255,255,255);" id="btn_submit">Submit data</button>

Answer 3

in echo_test.php return the echo statement or use die().
<?php
echo 'Hello ' . htmlspecialchars($_POST["firstname"]) . '!';
return;
?>