wp_send_json_error()

wp_send_json_error() — Sends a JSON response back to an Ajax request, indicating failure. If the $value parameter is a WP_Error object, the errors within the object are processed and output as an array of error codes and corresponding messages. All other types are output without further processing.

Inputs: $value (mixed): Optional. Data to encode as JSON, then print and die. Default null. $status_code (int): Optional. The HTTP status code to output. Default null. $flags (int): Optional. Options to be passed to json_encode(). Default 0.