PHP 实现类似js中alert() 提示框

/**
?* JS提示跳转
?* @param? $tip? 弹窗口提示信息(为空没有提示)
?* @param? $type 设置类型 close = 关闭,back=返回,refresh=提示重载,jump提示并跳转url
?* @param? $url? 跳转url
?*/
function alert($tip = "",$type = "",$url = "") {
??? $js = "<script>";
??? if ($tip)
??????? $js .= "alert('" . $tip . "');";
??? switch ($type) {
??????? case "close" : //关闭页面
??????????? $js .= "window.close();";
??????????? break;
??????? case "back" : //返回
??????????? $js .= "history.back(-1);";
??????????? break;
??????? case "refresh" : //刷新
??????????? $js .= "parent.location.reload();";
??????????? break;
??????? case "top" : //框架退出
??????????? if ($url)
??????????????? $js .= "top.location.href='" . $url . "';";
??????????? break;
??????? case "jump" : //跳转
??????????? if ($url)
??????????????? $js .= "window.location.href='" . $url . "';";
??????????? break;
??????? default :
??????????? break;
??? }
??? $js .= "</script>";
??? echo $js;
??? if ($type) {
??????? exit();
??? }
}