getting parsererror from presumed empty json response - php

Question

EL PROBLEMO
My JSON returns an associative array that I take elements from and display on the page. Sometimes one or more of the sub-arrays will be empty, and this is expected behavior. For those I want nothing displayed on the page. My problem is that currently anytime one of those sub-arrays is empty, I get a "parsererror". In my application, you switch between months, and this AJAX call is made when the dropdown selection is changed to a different month. On months where all the sub-arrays have values, I dont get an error. I only get it when one or more of the sub-arrays are empty.
PHP
first I perform the SQL queries, which I'm leaving out to keep this as short as possible, but these are the 3 resulting arrays:
$income = $results->fetchall(PDO::FETCH_ASSOC);
$expense = $results->fetchall(PDO::FETCH_ASSOC);
$recurring = $results->fetchall(PDO::FETCH_ASSOC);
Then I want to assign those to an array, which I then json_encode:
$array = array(
'income' => $income,
'expense' => $expense,
'recurring' => $recurring
);
echo json_encode($array);
AJAX
This is basically calling the previous php code, then displaying each record from the database in a table.
var request = $.ajax({
type: "POST",
url: 'inc/functions.php',
dataType: "JSON",
data: {action: "display_categories", cur_month:cur_month}
});
request.done(function(response){
$('#income tbody tr, #expense tbody tr').remove();
for(var i = 0; i < response.income.length; i++) {
$('<tr><td id="' + response.income[i].cat_id_PK + '">' + response.income[i].cat_name + '</td><td id="' + response.income[i].cat_id_PK +
'">$' + response.income[i].cat_amount + '</td></tr>').appendTo("#income");
}
for(var i = 0; i < response.expense.length; i++) {
$('<tr><td id="' + response.expense[i].cat_id_PK + '">' + response.expense[i].cat_name + '</td><td id="' + response.expense[i].cat_id_PK + '">$' + response.expense[i].cat_amount + '</td></tr>').appendTo("#expense");
}
for(var i = 0; i < response.recurring.length; i++) {
$('<tr><td id="' + response.recurring[i].cat_id_PK + '">' + response.recurring[i].cat_name + '</td><td id="' + response.recurring[i].cat_id_PK + '">$' + response.recurring[i].cat_amount + '</td></tr>').appendTo("#expense");
}
});
request.fail(function(jqxhr, textStatus){
alert("Request failed: " + textStatus);
});
};
JSON
Here's an example JSON response with two empty sub-arrays.
{
"income": [],
"expense": [],
"recurring": [
{
"cat_id_PK": 67,
"cat_name": "Grooming",
"cat_amount": "40.00",
"recur_begin": 1,
"recur_end": 12
}
]
}

Answer 1

Count the number of rows you get from sql query result.
if they are greater than 0 then send an extra field as
$d['status'] ='OK';
if no record exists then send the error handling as
$d['status'] ='ERR';
so check the status field in the data success
dataType: 'json',
data: you data,
success: function( data ) {
if(data.status == "OK"){
alert('success');
} else{
alert('failure');
}
}
});
try like this ,just to test and then use data