问如何显示retun调用所需的内容，而不是整个页面

EN

<?php 
$sContent.='<script src="https://code.jquery.com/jquery-1.12.4.js"></script>'; 
$sContent.='<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>'; 
$sContent.='<script src="in.js" type="text/javascript"></script>';

$id=2;
$sContent.='<div id="agree">Agree to terms: <input type="checkbox" id="agreed" value=1></div>';
$sContent.='<br><br><div class="show"></div>';

if($_GET['f'] == 'showInfo') 
{
   $sContent.=  'This is the info about item id: '.$_GET['id'];
}

$sAction = $_SERVER['PHP_SELF']."?id=".$id."&f=showInfo";
$sDest.= '<br><input class="'.$id.'" type="button" id="'.$id.'" name="'.$id.'" value="Click to show info about item '.$id.'" onClick="javascript:showInfo(\''.$sAction.'\');">';

$sContent.=  $sDest;
echo $sContent;
?>

function showInfo (action)
{

    var aryAction = action.split('?');
    params = aryAction[1];
    var theUrl = 'index.php';
    alert( aryAction[1]);
    $.ajax ({
        url: theUrl,
        data: params,
        async:true,
        success: function (data, textStatus)
        {
            $('.show').html (data);
        }
    }); 
}