Server Application Programming Interface (SAPI)

SAPI stands for Server Application Programming Interface. SAPI are the interface between PHP and a supporting platform, such as a web server (nginx, apache, caddy, … ), a debugger (phpdbg, …) or the command line interface (CLI).

<?php

echo PHP_SAPI;
echo php_sapi_name();

?>

Documentation

Related : Common Interface Gateway (CGI)