Question

As you can see I am retrieving JSON data from my ajax call but if the database can’t find anything it returns the print value of null.

e.g. print "null";

as you can see with case 1 I have asked it if it can not find obj.id then show this.

However as there is NO JSON being returned it should be if(data == "null") however it seems to work when I do that either.

I basically need it to notice that it could not find it, and to stop the script.

here is my jquery code.

    function fetch(e,formstring)
{

    $.ajax({
      type: 'POST',
      url: 'system/classes/core.php',
      data: formstring,
      dataType: 'json',
      contentType: "application/x-www-form-urlencoded;charset=utf-8",
      success: function(data){
          $.each(data, function(i, obj) {

               switch (e) { 
                 case 1:
                 if(!obj.id)
                 {
                    shownotify(1,"Sorry An error was found. Check Username / Password.");
                    alert("error");
                    shownotify(2,"");
                    return false;
                 }

                  $.each(obj, function(key, val) {
                     alert(key+" - "+val);
                  });


                 break;
                 case 2:
                 $.each(obj, function(key, val) {
                    if(val != 0)
                    {
                        $("#betataken").html("<span style='color:red'><b>"+betacode+"</b> - NOT VALID");
                    }
                    else
                    {
                        $("#betataken").html('<img src="theme/sysimages/tick.png"/><span style=" color: white;"><b>'+betacode+'</b> is valid</span');
                    }
                 });
                 break;
                 case 3:
                 $.each(obj, function(key, val) {
                     if(val != 0)
                     {
                        $("#usernametaken").html("<span style='color:red'><b>"+username+"</b> - is taken");  
                     }
                     else
                     {
                        $("#usernametaken").html('<img src="theme/sysimages/tick.png"/><span style=" color: white;"><b>'+username+'</b> is valid</span');
                     }
                     unamecheck = val;
                  });
                 break; 
                 case 4:
                 //LoginSript

                    $('#rightheader').html(obj.code);
                 break;
                 case 5:
                 //WelcomePage/Signup
                    $('#window').html(obj.code);
                 break;
               }
         });
      },
      error: function(data){
      $.each(data,function(i,myinfo){
            alert(i);       
          });
      },
      complete: function(){
        shownotify(2,"");  
      }
    });
    return false;
}

Answer 1

You could return null as json ($return['result'] = 'null'; in the php-file).
In your js:

[...]
dataType: 'json',
      contentType: "application/x-www-form-urlencoded;charset=utf-8",
      success: function(data){
      result = jQuery.parseJSON(data);
      if (result['result'] != 'null') {
          $.each(data, function(i, obj) {
              [...]