Google maps api geocoding is less accurate than manual search, why?

I am using php script (after this tutorial http://www.bitconsultants.net/2010/geocoding-with-google-maps-and-the-zend-framework/ ) to get the latitude and longitude of different addresses,

the problem is that if I manually search for the address on google maps, it gives me the correct location, when using php script the json response from google is even 500 meters from the manual search result, which makes it kind of meaningless for my needs ...

I pass the address in this format

$address = "{$data['street']}, {$data['postcode']}, {$data['city']}, {$data['province']}";

and I pass google key

Thank you