resolve ajax failure in codeigniter 3 view page?

Well, not sure about CI3 but with CI4 I would add :

Code:

<input type="hidden" class="txt_csrfname" name="<?= csrf_token() ?>" value="<?= csrf_hash() ?>" />

Code:

$(document).ready(function(){
        var csrfName = $('.txt_csrfname').attr('name'); // CSRF Token name
        var csrfHash = $('.txt_csrfname').val(); // CSRF hash
...


$.ajax({
            url : "your-url",
            method: "POST",
            data : {name:name, age:age, [csrfName]: csrfHash},
            success:  ...