All series on a given axis must be of the same data type

Question

I early had problems with formatting the time, but now having problem with showing the google chart visualiszation out of this error: All series on a given axis must be of t

Answer 1

Your column definitions are not correct: you want only 1 column for date & time, not two:

$table['cols'] = array(
    array('label' => 'Date & Time', 'type' => 'datetime'),
    array('label' => 'PH', 'type' => 'number'),
    array('label' => 'temperature','type' => 'number'), 
    array('label' => 'Chlorine','type' => 'number')
);