AJAX调用成功但在$ _POST ['sample']中抛出未定义的索引错误

Question

I have an AJAX call that passes data to another php file, createTest2.php, as below.

But the createTest2.php file throws error

Notice: Undefined index: sample in C:\xampp\htdocs\TestProj\Test\createTest2.php on line 2

caller.php

 $(document).ready(function(){
 $("#button_submit").click(function() 
 {

  $.ajax({
  type:"POST",
  url:"createTest2.php",
  data:{sample : "test"},
  success:function()
  {
    alert("success");
  }
});
});
});

createTest2.php

  <?php
       $test_name = $_POST['sample'];
       echo $test_name; 
?>

Answer 1

Total stab in the dark here but I'm guessing you have something like this

<form action="createTest2.php">
    <!-- some elements here -->
    <input type="submit" id="button_submit">
</form>

In which case, you should prevent the default action on the button, eg

$("#button_submit").on('click', function(e) {
    e.preventDefault();

    // and the rest of your ajax code
});

What's happening is your form's default method is GET and it is submitting normally, thus $_POST isn't populated.

Ideally, you should never blindly accept user input. I'd start with some checks in your PHP file

if (!isset($_POST['sample'])) {
    http_response_code(406);
    throw new Exception('sample data not submitted via POST');
}
$test_name = $_POST['sample'];

Secondly, catching click events on form submit buttons is rife with problems. For one, there's more than one way to submit a form. You should catch the form's submit event instead, eg

<form id="myForm" action="createTest2.php">
    <!-- etc -->
    <button type="submit">Go</button>
</form>

and the JS

$('#myForm').on('submit', function(e) {
    e.preventDefault();

    $.post(this.action, { sample: 'test' }).done(function(data) {
        alert('Success');
    });
});