PHP函数不适用于Ajax

Question

I have some button and on click JS for it:

<button id="trigger">Send</button>

and JS to invoke simple action

$('#trigger').on("click", function(event){ 
                    jQuery.ajax({
                        type: "POST",
                        url: 'functions.php',
                        dataType: 'json',
                        data: {functionname: 'add', arguments: [1, 2]},

                        success: function (obj, textstatus) {
                            alert('test success');
                        },
                        complete: function (obj, textstatus) {
                            alert('test complete');
                        }
                    });
                });

In above ajax I put functions.php with other simple function:

<?php

$message = "PHP Funtion Alert";
echo "<script type='text/javascript'>alert('$message');</script>";

?>

But, I got only alert invoked from alert('test complete'); How invoke alert from PHP file?

PS. this is only example. In PHP file will be some DB functions.

Answer 1

You're expecting JSON, hence the

dataType: 'json',

Yet, you're returning a script tag?

echo "<script type='text/javascript'>alert('$message');</script>";

And that's an error. What you want is to return valid JSON

$message = array("message" => "PHP Funtion Alert");
echo json_encode($message);

Then catch in the ajax function

jQuery.ajax({
  type     : "POST",
  url      : 'functions.php',
  dataType : 'json',
  data     : {
    data : 'to be sent'
  }
}).done(function(data) {
  console.log(data.message);
}).fail(function() {
    console.log(arguments);
});