PHP

jquery get data from php

You can read about ajax in javascript and make an ajax request that gets the json object from PHP then process that in your javascript:

Example (with some improvement to your PHP code)

PHP
  
$chart6 = $controller->runQuery("SELECT DATE(pay_date) `DATE`, SUM(amount) daily_amount, DATE_FORMAT(pay_date,'%a') DAYNAME FROM tbl_paid WHERE DATE(pay_date) BETWEEN DATE(:today) - INTERVAL 1 WEEK AND DATE(:today) GROUP BY DATE(pay_date);"); 
$chart6->execute(array(":today"=>$today));
$labels = array();
$series = array()
while($fetch = $stmt->fetch(PDO::FETCH_ASSOC)) {
  $labels[] = $fetch['DAYNAME'];
  $series0[] = $fetch['daily_amount'];
}
$series[] = $series0;

// add the labels and series to an array, then convert that to json
$data = array('labels' => $labels, 'series' => $series);
echo json_encode($data);

JS:

// Make an Ajax request, here I am using jQuery $.getJSON  but you can use $.get or $.post if you need to have it as a post request, or even $.ajax

$.getJSON('https://example.com/database_fetch_page.php', function(data) {
  new Chartist.Line('#headline-chart', data, options);
});