(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)
php_sapi_name — Returns the type of interface between web server and PHP
Returns a lowercase string that describes the type of interface (the Server API, SAPI) that PHP is using. For example, in CLI PHP this string will be "cli" whereas with Apache it may have several different values depending on the exact SAPI used. Possible values are listed below.
This function has no parameters.
   Returns the interface type, as a lowercase string,  or false on failure.
  
   Although not exhaustive, the possible return values include 
   apache, 
   apache2handler, 
   cgi (until PHP 5.3), 
   cgi-fcgi, cli, cli-server,
   embed, fpm-fcgi,
   litespeed, 
   phpdbg.
  
Example #1 php_sapi_name() example
     This example checks for the substring cgi
     because it may also be cgi-fcgi.
    
<?php
$sapi_type = php_sapi_name();
if (substr($sapi_type, 0, 3) == 'cgi') {
    echo "You are using CGI PHP\n";
} else {
    echo "You are not using CGI PHP\n";
}
?>
Note: An alternative approach
The PHP constant
PHP_SAPIhas the same value as php_sapi_name().
    The defined SAPI may not be obvious, because for
    example instead of apache it may be defined as 
    apache2handler.