php - How to check if an object is null or not? -

i´m trying condition if array nr#1 of xmlhttp.responsetext null. can not work. don´t know what´s wrong..

from php send array using json_encode. , in javascipt use json.parse() methode parse array.

there´re 2 strings in array ["", ""]

and i´m trying detect if first array null alert something.

let´s see code :

var str=xmlhttp.responsetext; var res=json.parse(str); 

and following lines have tried none of them ´s working !

if (res[0]=null) { alert('hey, it´s null'); }  ,  if (res[0]==null) { alert('hey, it´s null'); }  ,  if (res[0]=="null") { alert('hey, it´s null'); }  ,  if (res[0]=="") { alert('hey, it´s null'); }   have used php echo code json , get:  ["null",""] 

so what´s wrong ?

if json data :

["null",""] 

which implies

$data = array(     0 => "null",     1 => "" );  $json = json_encode($data); echo $json;                 ---> result yours....["null",""] echo "<br />"; $res =  json_decode($json);   ----> must decode json first...  echo $res[0];                -----> code result "null" wanted... 

the below statement let know if object empty.

if (res[0]==null) {             -----> result "[" not data "null".... alert('hey, it´s null'); } 

so, firstly must decode json data , next check object.