raspap-webgui/ajax/logging/clearlog.php

<?php

require_once '../../includes/config.php';
require_once '../../includes/functions.php';

if (isset($_POST['logfile'])) {
    $logfile = $_POST['logfile'];

    // truncate requested log file
    exec("sudo truncate -s 0 $logfile", $return);
    echo json_encode($return);
}