jQuery - 如何将带有ajax的数组传递给PHP？

$.ajax({
            type:"get",
            url:"add/sql_customer.php",
            data:   "?title="+title+
                    "&customerid="+cid+
                    "&action=savecontract",

            success:function(data){
            }
        });

I want to post titles as an array.. How can I do that?? I get always undefined or an empty variable.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" id="title" name="title[]" placeholder="Titel-1"/>
<input type="text" id="title" name="title[]" placeholder="Titel-2"/>
<input type="text" id="title" name="title[]" placeholder="Titel-3"/>

</div>

You get the entered titles through an iteration over the input elements with class title-container:

$('#btn-submit').click(function(){
    var titles = [];
    
    $('.title-container').each(function(){
        titles.push($(this).val());
    });

    console.log(titles);
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<input type="text" class="title-container" placeholder="Title 1"/>
<input type="text" class="title-container" placeholder="Title 2"/>
<input type="text" class="title-container" placeholder="Title 3"/>

<button id="btn-submit">Get titles</button>

</div>