php google weather error handling issue - php

Question

I have a php script that interacts with the google weather api.Everything works ok, but if I test it with a false location like "blahblah" I get a slew of errors in the browser despite having some validation in my script. The php code is as follows:
<?php
function googleWeather($location){
$url = "http://www.google.com/ig/api?weather=" . urlencode($location);
$xml = simplexml_load_file($url);
$current_conditions = $xml->xpath("/xml_api_reply/weather/current_conditions");
$temp_c = $current_conditions[0]->temp_c['data'];
$temp_f = $current_conditions[0]->temp_f['data'];
$result = sprintf("Current temperature is %s° Celsius %s° Fahrenheit",$temp_c,$temp_f);
return $result;
}
$loc = "blahblah";
$goog = googleWeather($loc);
if($goog == false){
echo "An error occurred";
}
else{
echo $goog;
}
?>
The error that is rendered in the browser is as follows:
( ! ) Notice: Undefined offset: 0 in C:\wamp2\www\phpAcademy\GoogleWeatherApi\TMP5c2a1z4emd.php on line 11
Call Stack
# Time Memory Function Location
1 0.1086 370080 {main}( ) ..\TMP5c2a1z4emd.php:0
2 0.1086 370184 googleWeather( ) ..\TMP5c2a1z4emd.php:23
( ! ) Notice: Trying to get property of non-object in C:\wamp2\www\phpAcademy\GoogleWeatherApi\TMP5c2a1z4emd.php on line 11
Call Stack
# Time Memory Function Location
1 0.1086 370080 {main}( ) ..\TMP5c2a1z4emd.php:0
2 0.1086 370184 googleWeather( ) ..\TMP5c2a1z4emd.php:23
( ! ) Notice: Undefined offset: 0 in C:\wamp2\www\phpAcademy\GoogleWeatherApi\TMP5c2a1z4emd.php on line 12
Call Stack
# Time Memory Function Location
1 0.1086 370080 {main}( ) ..\TMP5c2a1z4emd.php:0
2 0.1086 370184 googleWeather( ) ..\TMP5c2a1z4emd.php:23
( ! ) Notice: Trying to get property of non-object in C:\wamp2\www\phpAcademy\GoogleWeatherApi\TMP5c2a1z4emd.php on line 12
Call Stack
# Time Memory Function Location
1 0.1086 370080 {main}( ) ..\TMP5c2a1z4emd.php:0
2 0.1086 370184 googleWeather( ) ..\TMP5c2a1z4emd.php:23

Answer 1

Google returns the following for an invalid location
<xml_api_reply version="1"><weather module_id="0" tab_id="0" mobile_row="0" mobile_zipped="1" row="0" section="0"><problem_cause data=""/></weather></xml_api_reply>
This xml doesnt have the element "current_conditions" inside "weather". Thats casusing the error.
Check if exists then proceed which can be done with some thing like
if($current_conditions){
// you code here
} else {
return false;
}

Answer 2

I replaced blahblah with real city and it started to work.
Probably you enter your city address with wrong syntax.
Try to change your location, for example Zurich

Answer 3

The errors are pretty self-explanatory, $current_conditions doesn't contain what you think it does:
$current_conditions = $xml->xpath("/xml_api_reply/weather/current_conditions");
$temp_c = $current_conditions[0]->temp_c['data'];
// ^^^ undefined index
$temp_f = $current_conditions[0]->temp_f['data'];
// ^^^ Trying to access property of non object
You are not validating the result of $current_conditions:
if (is_array($current_conditions) && isset($current_conditions[0]))
{
$temp_c = $current_conditions[0]->temp_c['data'];
$temp_f = $current_conditions[0]->temp_f['data'];
}
Furthermore, you may need to validate the existence of the object properties, as well as the existence of the data key in those properties:
if (is_array($current_conditions) && isset($current_conditions[0]))
{
$cur = $current_conditions[0];
if (isset($cur->temp_c) && isset($cur->temp_c['data']))
{
$temp_c = $cur->temp_c['data'];
}
if (isset($cur->temp_f) && isset($cur->temp_f['data']))
{
$temp_f = $cur->temp_f['data'];
}
}
This is quite verbose, but to be absolutely sure to avoid these notices - it's what you have to do. You can and should turn off error reporting once you go live with your application. Notices are meant to help you debug code, if you understand how they're being generated and can safely ignore them, it may be OK.
And, if you feel confident that you know the API will return FALSE for an invalid query, just check if $current_conditions === FALSE and you can skip all the extra validation.