If checked - write to file

testwrite_wp.php

function dpr_checkbox() {
    global $dpr_option_name, $dpr_options;
    if(is_array($dpr_options) && $dpr_options['disable'] == '1'){
        echo "ON";
        $file = site_url()."/"."license.txt";
        $f = fopen('new.php', 'a+') or die('error open file');
        for ($i=0; $i < 3; $i++){
            fputs($f,"\n$i");
        }   
        fclose($f);
    }

}
add_action( 'dpr_checkbox', 'dpr_checkbox' );