Unable to pass Value from PHP to AJAX - php

Question

I have a problem with the communication between AJAX and PHP. I've already tried all these pieces of code from related questions and answers but nothing worked. This code should recieve a JSON string from a PHP file on the same server and display the values in the HTML area.
$(document).ready(function(){
setInterval(ajaxcall, 1000);
});
function ajaxcall(){
var data = $('#signup_form').serialize();
$.ajax({
type: "GET",
url: "test.php",
data: data,
dataType: 'json',
success: function (data) {
window.console.log("Success");
document.getElementById("count").innerHTML = $('#time').html(data.time);
},error: function alert(){"error";}
});}
When I execute the script in my browser (with debug mode) then nothing happens. I assume this implies a problem with the 'success' method.
Here is a part of my PHP code (for testing):
for($i = 0; $i < 50; $i++){
sleep(1);
return_json($argv[1]);
}
//return all values for html/javascript
function return_json($a){
$json = array('time' => $a);
echo json_encode($json);
}
I hope some of you can help me :)

Answer 1

Is the function ajaxcall() really being called? Try to add a console.log call at its begining, eg
function ajaxcall(){
var data = $('#signup_form').serialize();
console.log(' form data = %o', data)
//...
There is another possible issue the function error: function alert(){"error";} does nothing visible. If your server script is returning an error you will see nothing in this case.
Change it to something like
error: function(){ alert("error"); }

Answer 2

You should add the content type to your response header:
//this line
header('Content-type: application/json');
for($i = 0; $i < 50; $i++){
sleep(1);
return_json($argv[1]);
}
//return all values for html/javascript
function return_json($a){
$json = array('time' => $a);
echo json_encode($json);
}
Further reading and a more detailed explanation here: jQuery $.ajax request of dataType json will not retrieve data from PHP script