JSON result not working correctly with jQuery in PHP code

Question

I have a JSON data that is returned by AJAX:

PHP file:

//SQL: fetch result if user exist
    $result = array("Name"=>$name, "ID"=>$id, "Age"=>$age, "School"=>$school, "Department"=>$dept);
    echo json_encode($result);
//else return error
    $error = 'No record for this user.';
    $result = array("Error"=>$error);
    echo json_encode($result);

jQuery AJAX:

//AJAX result
request.done(function( msg ):
//alert( msg ); working fine for users who exist and even those who doesn't exist.
var detail = jQuery.parseJSON( msg );
 if ( detail.Name.length > 0 ){
      $('.student').slideDown(300);
      $('.student').html(detail.Name);
      // this is working fine
    }
 if ( detail.Error.length > 0 ){
     $('.student').slideDown(300);
     $('.student').html(detail.Error); 
     //this is not working even if the user does not exist.
    }

How do I come around this?

What does console.log( detail ); give you if you call it inside the Error segment? — hjpotter92
– hjpotter92, Commented Apr 15, 2014 at 13:12
@Khôi: the echo is just once. It echoes once based on the condition that is met: whether a student found in the DB or not. — Yax
– Yax, Commented Apr 15, 2014 at 13:17
Using chrome and console.log(detail) you can see the object and it's properties. — Milen Georgiev
– Milen Georgiev, Commented Apr 15, 2014 at 13:29

patrick · Accepted Answer · 2014-04-15 14:52:49Z

2

Your scripting will fail at the moment you're checking detail.Name.length. The error will stop Javascript from executing the rest.

In case of an error your JSON data will look like this:

   {"Error":"No record for this user."}

if you then run your JavaScript code:

if(detail.Name.length>0)

... Javascript will come back with "Uncaught TypeError: cannot read property 'length' of undefined..." and it will STOP EXECUTING all other JavaScript code, thus it never gets to your error handler.

to solve this, don't check the length of a record before you know it exists:

if(typeof detail.Name!="undefined" && detail.Name.length>0){
   ... etc...

In this case you don't even have to check the lenth, if "name" is set you know it was set by your PHP script...

answered Apr 15, 2014 at 14:52

patrick

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hjpotter92 Over a year ago

Alternatively, 'Error' in detail and 'Name' in detail

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