Data send in json is change while send it - php

Question

$.ajax({
type : 'POST',
url : '<?=site_url("aplikasi_tambah_merchant/input_merchant/get_mdr_master");?>',
data : 'kode='+arr_value[0],
beforeSend:function(){
$('#ajax-loader').show();
},
error: function(){
$('#ajax-loader').hide();
alert('Error\nGagal request data');
},
success: function(data){
var res = JSON.parse(data);
datamdr = Number(res.mdr_debit);
$('#ajax-loader').hide();
}
});
$.ajax({
type : 'POST',
url : '<?=site_url("pameran/update_mdr_pameran");?>',
data : 'datamdr='+datamdr+'&app_id='+app_id+'&on_off=2',
beforeSend:function(){
$('#ajax-loader').show();
},
error: function(){
$('#ajax-loader').hide();
alert('Error\nGagal request data');
},
success: function(data){
alert("tes "+datamdr);
alert("balik "+data);
$('#ajax-loader').hide();
}
});
this is the ajax code to send my data.
the first ajax is to get the value of datamdr = Number(res.mdr_debit);then i send datamdr value again to the controller, but in controller here
public function update_mdr_pameran() {
$this->config->set_item('compress_output', FALSE);
$datamdr = trim($this->input->post('datamdr'));
$app_id = trim($this->input->post('app_id'));
$on_off = trim($this->input->post('on_off'));
$out = $this->aplikasi_model->update_mdr_app_id_onoff($datamdr, $app_id, $on_off);
echo json_encode($datamdr);
}
those datamdr value is undefined, while the other 2 variable is still readable as string? how is it possible? i've tried parse the first json to string and int but still no luck to send the data again

Answer 1

Ajax works asynchronously by default so what is happening, is that both your requests execute at the same time and at that moment, the value you set on completion of the first ajax call, is still undefined.
You should wrap your second ajax call in a function and call that from the success handler in your first ajax call.
Or you combine both requests in one as they seem to be going to the same server any way.
A third option would be to make the ajax calls synchronous but that would block the execution of your script so I would not recommend that.

Answer 2

What #jeroen suggesting is this:
$.ajax({
type : 'POST',
url : '<?=site_url("aplikasi_tambah_merchant/input_merchant/get_mdr_master");?>',
data : 'kode='+arr_value[0],
beforeSend:function(){
$('#ajax-loader').show();
},
error: function(){
$('#ajax-loader').hide();
alert('Error\nGagal request data');
},
success: function(data){
var res = JSON.parse(data);
datamdr = Number(res.mdr_debit);
$('#ajax-loader').hide();
update_mdr_pameran();
}
});
function update_mdr_pameran(){
$.ajax({
type : 'POST',
url : '<?=site_url("pameran/update_mdr_pameran");?>',
data : 'datamdr='+datamdr+'&app_id='+app_id+'&on_off=2',
beforeSend:function(){
$('#ajax-loader').show();
},
error: function(){
$('#ajax-loader').hide();
alert('Error\nGagal request data');
},
success: function(data){
alert("tes "+datamdr);
alert("balik "+data);
$('#ajax-loader').hide();
}
});
}