Ext Js ajax request not working for failure function - extjs

Question

here is my function sending ajax request for checking email duplication while getting response from my php file , not falling on failure function it returns only in success function , for this i have checked result.responseText == to "false" and with else condition now in this condition it shows the error popup message too but donot abort the request continuoues its execution and saves the data
function email_check(userType) {
//alert(userType);
var extmail= Ext.Ajax.request({
url: '<?= Extjs_renderer::ajaxurl();; ?>ajax/emailcheck',
success: function ( result, request ) {
if(result.responseText=='false'){
//Ext.Ajax.abort(extmail); tried
Ext.MessageBox.alert('Error', "email already exist");
// return false;
//Ext.getCmp('email').setValue(''); works
}else {
return true;
}
},
failure: function(response, options) {
Ext.MessageBox.alert('Error', "email already exist fail");
},
params: {merc_mem_tab:userType }
});
}
here is my ajax.php code
function emailcheck(){
$get_email=$this->db->query("select * from customers where email='".$_REQUEST['merc_mem_tab']."'");
if($get_email->num_rows==0){
echo "true";
return true;
}else{
echo "false";
// echo "{success: true}";
return false;
}
}
while on my panel handler i am also trying to check the response but could not succeeded
if('<?= $this->controller->name; ?>'=="customers"){
//alert(Ext.getCmp('email'))
if(email_check(Ext.getCmp('email').getValue()) == false){
return false;
}
}

Answer 1

You can't return from an ajax request, It is asyncron, and this bit of code if(email_check(Ext.getCmp('email').getValue()) == false) won't wait for the answer.
Also the failure is as Imad said, just for http failures not for false responses. your code to check for response false was correct but i suggest you call a saving method on the success function.Like:
function email_check(userType) {
//alert(userType);
var extmail= Ext.Ajax.request({
url: '<?= Extjs_renderer::ajaxurl();; ?>ajax/emailcheck',
scope: this,
success: function ( result, request ) {
if(result.responseText=='false'){
Ext.MessageBox.alert('Error', "email already exist");
//do nothing else
}else {
this.saveData();
}
},
failure: function(response, options) {
Ext.MessageBox.alert('Error', "Communication failed");
},
params: {merc_mem_tab:userType }
});
}

Answer 2

The choice of success or failure callback is based on the HTTP response code. So, if you want to reach the failure function, you'll have to do some :
function emailcheck(){
$get_email=$this->db->query("select * from customers where email='".$_REQUEST['merc_mem_tab']."'");
if($get_email->num_rows==0){
echo "true";
return true;
}else{
throw new Exception("Error : Email Already Exists !");
}
}
It should provoke an error 500 (exception unhandled) and ExtJS will identify it as a failure response.