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Forcing an error in an AJAX call

by | Dec 20, 2014 | Reference, Technical

When calling AJAX from Javascript, callbacks of ‘success’ and ‘error’ are typically supported.  Your call might look something like this (I happen to be using Angular here):

$http( request ).success( function( response ) {
   console.log( 'SUCCESS: ' + response );
}).error( function( response ) {
   console.log( 'ERROR: ' + response );
});

 

Your server code, possibly written in PHP, might look something like this:

function some_code_here()
{
   echo 'everything is cool';
   exit;
}

 

No matter what, the ‘success’ callback is always triggered.  So, how would you trigger the ‘error’ callback?  Hmm.  This had me reeling for a bit.  Then found that this works:

function some_code_here()
{
   $whatever = true;
   if ( $whatever )
   {
      header( 'HTTP/1.1 500 Internal Server Error' );
      echo 'some error happened';
      exit;
   }
}

 

You can return any error value that you see on this page:

http://en.wikipedia.org/wiki/List_of_HTTP_status_codes#4xx_Client_Error

 

The process of forcing an error is completely not intuitive, which is why I’ve posted it here for future reference.  Hope it helps you too.