function.php

<?php

function writeFile($fullpath, $content)
{
    if (is_writable($fullpath)) {

        if ($fp = fopen($fullpath,'w')) {
 
            if (fwrite($fp,$content)) {

                // ...

            } else {
                return false;
            }
        } else {
            return false;
        }
    } else {
        return false;
    }
}