Change Limit Size File Uploads

/* For Change Limit Size File Uploads */
function increase_upload_size_limit() {
    $user = wp_get_current_user();
    $roles = (array) $user->roles;

    if ($roles[0] == 'administrator') {
        return 1048576 * 15; // 15 MB
    }

    if ($roles[0] == 'editor') {
        return 1048576 * 4; // 4 MB
    }

    if ($roles[0] == 'author') {
        return 1048576 * 4; // 4 MB
    }
}

add_filter( 'upload_size_limit', 'increase_upload_size_limit', 99 );