DETAILS
I\'d like to make use of mysql\'s spatial extension, so I am trying to store longitude and latitude in a mysql table of datatype POINT using
Note that parameterizing queries is not (simple) string replacement. In your code your query parameter is put in a string literal which will be kept untouched.
Try this:
$location = 'POINT(' . $latitude . " " . $longitude . ')';
$sql = "INSERT INTO my_geodata SET location = PointFromText(:location)";