HI ALL!!!
I`m new on this forum and in JS too...
please help me...

I`m trying to send form data with POST via AJAX to PHP
I`m using JQXWidgets...

I have created a JQXwibdow

HTML Code:
div id="add_new_user">
	<div id="add_new_userHeader">
    	<span>
        	<img src="img/icons/add.png" style="margin-right: 15px;">
            <span id="add_new_userHead_name"></span>
		</span>
	</div>
    <div id="add_new_userContent" style="overflow: hidden;">
        <form method="post" id="add_user" autocomplete="off">
            <input type="text" id="add_username" style="margin:5px;"/>
            <input type="password" id="add_psw" style="margin:5px;"/>
            <input type="password" id="ret_add_psw" style="margin:5px;"/>
            <div id="company" style="margin:5px;"></div>
            <div id="group" style="margin:-33px 0 0 185px;"></div> 
            <div id='add_birth' style="margin:-28px 0 0 360px; float:left;"></div>    
            <input type="text" id="add_fname" style="margin:10px 5px 5px;"/>
            <input type="text" id="add_mname" style="margin:5px;"/>
            <input type="text" id="add_lname" style="margin:5px;"/>
            <div id="selectiongend" style="float: left;font-size: 13px;font-family: Verdana;margin:5px;">
                <div id='add_gend_man' style="margin:5px;"><span id="add_gendman"></span></div>
                <div id='add_gend_woman' style="margin:-22px 0 5px 60px;"><span id="add_gendwoman"></span></div>
            </div>            
            <input type="submit" style="margin:5px; float:left;" id="add_new_usrbtn" onClick="_addEventListeners()"/>
        </form>
    </div>
</div>
with the button click function I`m trying to send this form data to PHP talk file...
I need this file to talk over php OOP and js

Code:
$('#add_new_usrbtn').click(function (e) {
	e.preventDefault();
	var psw2 = document.getElementById('ret_add_psw').value;
	dataString = 'action=' + 'newuser' + '&usr=' + $('add_username').val() + '&psw=' + $('add_psw').val() + '&fname=' + $('#add_fname').val()  + '&lname=' + $('add_lname').val() + '&mname=' + $('add_mname').val() + '&' + $('form#add_user').serialize(e);
	$.ajax({
		type: "POST",
		url: "system/talk.php",
		data: dataString,
		dataType: "html",
		cache: false,
		beforeSend: function(data){
			alert(data);},
		error: function(data){
			alert(data);},
		success: function(data){
			alert(data);
		}													   
	}); 
	return false;  
});
and in talk.php I have this code

PHP Code:
if ($_POST['action'] === 'newuser')
            {
                    
$username $_POST['usr'];
                    
$password $_POST['psw'];
                    
$company $_POST['company'];
                    
$birth $_POST['add_birth'];
                    
$group $_POST['group'];
                    
$fname $_POST['add_fname'];
                    
$mname $_POST['add_mname'];
                    
$lname $_POST['add_lname'];
                    if (
$_POST['add_gend_man'] = true){
                        
$gender 'M';
                    } elseif(
$_POST['add_gend_woman'] = true){
                        
$gender 'F';
                    } else { echo 
'მოხდა შეცდომა';}
                
$salt $account->salt_code();
                
$email_code $email->email_code();
                
$result $account->creat_acc($username,$password,$company,$birth,$group,$fname,$mname,$lname,$gender,$salt,$email_code);
                echo 
$result;
            } 
but in php data is 0

when I`m trying to echo any of them
ex. $fname
it said me that the variable is null
and I can not write nullable variable`s value in my db

please help me

what is wrong in my code???
I do not understand...

please help me!!!