[Chartjs]-How to pass values to a chart (chart.js / morris.js)

Try to change your xkey and ykeys. Because your actual cron_time and images_processed doesn’t exist in your json data.

xkey: 'x', // 'cron_time',
ykeys: ['y'], //['images_processed'],

Or change the keys in your php and keep the actual Morris config:

array
(
    'cron_time' => $row['sales'],
    'images_processed' => $row['quantity'],
)

You should also convert your quantity to int or float:

(int)$row['quantity']
(float)$row['quantity']