How does the PHP interface call the return value to the C # Program in json format? Return or echo

How does the PHP interface call the return value to the C # Program in json format? Return or echo to solve the problem !!! How does the PHP interface call the return value to the C # Program in json format? Is return or echo? is return returned?
Does echo work?

Reply to discussion (solution)

Of course it's echo.

Return can only be used inside php
For external users, if you want to parse data for others, you can understand the output and use echo

Exit (content to be output)

Of course it is echo. if it is json, it is best to add the header id.

 'Fdipzone '); header ('content-type: application/json; charset = utf8'); echo json_encode ($ ret);?>

Echo or print_r.