Chartjs-How to use a string returned from php by ajax as data for a chart.js chart?

try

data: val.dataset.data 

rather than

data: val

It appears you’re just popping the entire json into the val field, rather than isolating the data portion needed for plotting

The problem was that the response from php was actually a string. Chart() requires data to be an object, so constructing an array in php with relevant data and using json_encode() allowed the data property to be filled with values from the server.