WordPress at a glance
function is not described

_ajax_wp_die_handler() WP 3.4.0

Kills WordPress execution and displays Ajax response with an error message.

This is the handler for wp_die() when processing Ajax requests.

No Hooks.

Return

Nothing (null).

Usage

_ajax_wp_die_handler( $message, $title, $args );
$message(string) (required)
Error message.
$title(string)
Error title (unused).
Default: ''
$args(string/array)
Arguments to control behavior.
Default: empty array

Code of ajax wp die handler: wp-includes/functions.php WP 5.2

<?php
function _ajax_wp_die_handler( $message, $title = '', $args = array() ) {
	// Set default 'response' to 200 for AJAX requests.
	$args = wp_parse_args(
		$args,
		array( 'response' => 200 )
	);

	list( $message, $title, $r ) = _wp_die_process_input( $message, $title, $args );

	if ( ! headers_sent() ) {
		// This is intentional. For backward-compatibility, support passing null here.
		if ( null !== $args['response'] ) {
			status_header( $r['response'] );
		}
		nocache_headers();
	}

	if ( is_scalar( $message ) ) {
		$message = (string) $message;
	} else {
		$message = '0';
	}

	if ( $r['exit'] ) {
		die( $message );
	}

	echo $message;
}