how to check for success in curl

[dadamssg]

i want to check if my function is a success or not using bit.ly's API. im using this function i found on the web.

   1. /* Example code */  
   2. $link = "http://www.x-pose.org";  
   3.   
   4. print getSmallLink($link);  
   5.   
   6. function getSmallLink($longurl){  
   7. // Bit.ly  
   8. $url = "http://api.bit.ly/shorten?version=2.0.1&longUrl=$longurl&login=YOURLOGIN&apiKey=YOURAPIKEY&format=json&history=1";  
   9.   
  10. $s = curl_init();  
  11. curl_setopt($s,CURLOPT_URL, $url);  
  12. curl_setopt($s,CURLOPT_HEADER,false);  
  13. curl_setopt($s,CURLOPT_RETURNTRANSFER,1);  
  14. $result = curl_exec($s);  
  15. curl_close( $s );  
  16.   
  17. $obj = json_decode($result, true);  
  18. return $obj["results"]["$longurl"]["shortUrl"];  
  19. }  

if this snippet goes write i get my bit.ly url and Tweet the results. But sometimes it times out. How would i write something to check if it returned a bit.ly url and if not execute some other code?