php通过json实现前后端数据传值

<script src="js/jquery-3.3.1.min.js"  type="text/javascript"></script>
    <script>
    $(function(){
        $("#btn").click(function(){
                var my_data="前端变量";            
                $.ajax({
                    url: "translate.php",  
                    type: "POST",
                    data:{trans_data:my_data},
                    error: function(){  
                        alert('');  
                    },                   
                    complete:function()
                    {
                        //location.href = "index.php?trans_data=" + my_data;
                    },  
                    success: function(data){//如果调用php成功                                                
                        var dataObj=eval("("+data+")");
                        alert(dataObj.name);
                    } 
                });
        });            
    });     
    </script>
......
<form action="translate.php" method="post">
      <input type="text" name="title" value="标题"/>
      <input id="btn" type="button" value="点击"/>
</form>

<?php
    header('Content-Type: text/html; charset=UTF-8'); 
    $backValue=$_POST['trans_data'];
    $info = array('name' =>'张三','sex'=>'男');
    if(isset($backValue)){
        echo json_encode($info);
    }