CakePHPに空間データを保存する

この行を変換します：

$this->data['Report']['position'] = $db->expression("GeomFromText('POINT(" . 
    $this->data['Report']['lat'] . " " . $this->data['Report']['lng'] . ")')");

to：

$this->data['Report']['position'] = (object) $db->expression("GeomFromText('POINT(" .
     $this->data['Report']['lat'] . " " . $this->data['Report']['lng'] . ")')");

動作するはずです。