check_ajax_referer()

check_ajax_referer() — Verifies the Ajax request to prevent processing requests external of the blog.

Inputs: $action (int|string): Action nonce. $query_arg (false|string): Optional. Key to check for the nonce in $_REQUEST (since 2.5). If false, $_REQUEST values will be evaluated for ‘_ajax_nonce’, and ‘_wpnonce’ (in that order). Default false. $stop (bool): Optional. Whether to stop early when the nonce cannot be verified. Default true.

Returns int|false: 1 if the nonce is valid and generated between 0-12 hours ago, 2 if the nonce is valid and generated between 12-24 hours ago. False if the nonce is invalid. Only possible when $stop is false, as the function otherwise exits rather than returning false.