<?php
    // ...
    public function set($collection="My Friendly Sheet Name",$sheet="",$range="",$values=array()) {
        $result = [];

        $keys   = array("collection","sheet","range","values");
        foreach ($keys as $k) {
            $$k = (isset($_GET[$k])) ? $_GET[$k]:$$k;
            if (!$$k) $result = ["success"=>false,"msg"=>"Missing key: $k"];
        }
        if (gettype($values)=="string") {
            $b64    = base64_decode($values);
            if ($b64)   $values = json_decode(unserialize($b64),true);
            else        $values = json_decode($values,true);
        }
        if (!$values) $result = ["success"=>false,"msg"=>"Invalid value array provided"];

        if (!$result) {
            $spreadsheetId = $this->collection[$collection];
            $range  = "$sheet!$range";
            $_values = new Google_Service_Sheets_ValueRange();
            $_values->setValues($values);
            $_values->setMajorDimension("ROWS");
            $options = ["valueInputOption" => "RAW"];
            $res = $this->_sheets->spreadsheets_values->update($spreadsheetId,$range,$_values,$options);

            if ($res->spreadsheetId) $result = ["success"=>true,"msg"=>sprintf("Updated %d cells",$res->updatedCells)];
        }

        echo json_encode($result);
    }
// ...
?>