php code does not execute

I want to execute a PHP code from VS.code on Debian OS. I'm sure the Apache is installed and active. I'm sure the PHP is installed. I'm sure about the php.executepath is correct. when I navigate to locallhost/ping.php the web page is loading but when I want to enter the IP and ping it there isn't any result on the page! this is my code: ping '.shell_exec(($cmd)).'

';
           }
        ?>
        
            IP :