我的ajax函数未在某些视图中运行

Question

我的ajax在添加乘客视图中不起作用，但是当我在其他视图（例如添加组乘客）上尝试时，它就起作用了。我正在使用Codeigniter。

这是我的ajax：

$(document).ready(function(){
        $("#destination").change(function(){
            var destination = $("#destination").val();
            var region = $("#region").val();

            $.ajax({
                url: 'http://localhost/ci-travel2.0/passanger/getdateprice/',
                type: 'POST',
                dataType: 'json',
                data: {
                    destination : destination,
                    region : region
                },
                success: function (data) {
                    $("#date_tour").val(data.date_tour);
                    if((<?= $this->session->userdata('jumlah_pax') ?>) && (<?= $id_user ?> >= 1)) {
                        $("#price_invoice").val(data.price*<?= $this->session->userdata('jumlah_pax') ?>-500000*<?= $this->session->userdata('jumlah_pax') ?>);
                    } else if((<?= $this->session->userdata('jumlah_pax') ?>) && (<?= $id_user ?> <= 0)){
                        $("#price_invoice").val(data.price*<?= $this->session->userdata('jumlah_pax') ?>-250000*<?= $this->session->userdata('jumlah_pax') ?>);
                    } else if((<?= $id_user ?>) >= 1 && !(<?= $this->session->userdata('jumlah_pax') ?>)){
                        $("#price_invoice").val(data.price-500000);
                    } else if((<?= $id_user ?>) <= 0 && !(<?= $this->session->userdata('jumlah_pax') ?>)){
                        $("#price_invoice").val(data.price-250000);
                    } 
                }
            });
        });
    });

这是我的第一个视图（附加乘客）

<div class="col-md-12">
                <form action="<?= base_url('passanger/addpassanger') ?>" method="POST" enctype="multipart/form-data">
                <div class="form-row">
                    <div class="col-md-3">
                    <label for="region">Region</label>
                        <select name="region" id="region" class="select2-input region form-control" style="width:100%;">
                            <option value="">-- Select Region --</option>
                            <?php foreach($region as $r) : ?>
                            <option value="<?= $r['id_region'] ?>"><?= $r['region'] ?></option>
                            <?php endforeach; ?>
                        <?= form_error('region', '<small class="text-danger pl-3">', '</small>'); ?>
                        </select>
                    </div>
                    <div class="col-md-3">
                        <label for="destination">Destination</label>
                            <select name="destination" id="destination" class="select2-input destination form-control" style="width:100%;">
                                <option value="">-- Select Destination --</option>
                                <?php foreach($destination as $d) : ?>
                                <option value="<?= $d['id_destination'] ?>"><?= $d['destination'] ?></option>
                                <?php endforeach; ?>
                            <?= form_error('destination', '<small class="text-danger pl-3">', '</small>'); ?>
                            </select>
                    </div>
                    <div class="col-md-3">
                        <label for="date_tour">Tanggal Keberangkatan</label>
                        <input type="text" class="form-control" id="date_tour" name="date_tour" readonly>
                        <?= form_error('date_tour', '<small class="text-danger pl-3">', '</small>'); ?>
                    </div>
                    <div class="col-md-3">
                        <label for="price">Price Invoice</label>
                        <input type="text" class="form-control" id="price_invoice" name="price_invoice" readonly>
                        <?= form_error('price_invoice', '<small class="text-danger pl-3">', '</small>'); ?>
                    </div>
                </div>

这是我的第二个观点（组乘客）

div class="col-md-12">
                <form action="<?= base_url('passanger/addgroup') ?>" method="POST" enctype="multipart/form-data">
                <div class="form-row">
                    <div class="col-md-3">
                        <label for="region">Region</label>
                        <select name="region" id="region" class="select2-input region form-control" style="width:100%;">
                            <option value="">-- Select Region --</option>
                            <?php foreach($region as $r) : ?>
                            <option value="<?= $r['id_region'] ?>"><?= $r['region'] ?></option>
                            <?php endforeach; ?>
                        <?= form_error('region', '<small class="text-danger pl-3">', '</small>'); ?>
                        </select>
                    </div>
                    <div class="col-md-3">
                        <label for="destination">Destination</label>
                            <select name="destination" id="destination" class="select2-input destination form-control" style="width:100%;">
                                <option value="">-- Select Destination --</option>
                                <?php foreach($destination as $d) : ?>
                                <option value="<?= $d['id_destination'] ?>"><?= $d['destination'] ?></option>
                                <?php endforeach; ?>
                            <?= form_error('destination', '<small class="text-danger pl-3">', '</small>'); ?>
                            </select>
                    </div>
                    <div class="col-md-3">
                        <label for="date_tour">Tanggal Keberangkatan</label>
                        <input type="text" class="form-control" id="date_tour" name="date_tour" readonly>
                        <?= form_error('date_tour', '<small class="text-danger pl-3">', '</small>'); ?>
                    </div>
                    <div class="col-md-3">
                        <label for="price">Price Invoice</label>
                        <input type="text" class="form-control" id="price_invoice" name="price_invoice" readonly>
                        <?= form_error('price_invoice', '<small class="text-danger pl-3">', '</small>'); ?>
                    </div>
                </div>

两种观点之间没有区别（我认为），为什么一种有效而另一种无效？