PHP如何读取由JavaScript设置的Cookie

<?php
// 读取JavaScript设置的cookie
header("Content-type: text/html; charset=utf-8");
if(isset($_COOKIE["param"])){
 echo $_COOKIE["param"];
}
?>
<script type="text/javascript"> 
function $_cookie(name,value){
 var date = new Date(); 
 $livetime = 52436001000;// cookie生命周期
 date.setTime(date.getTime()+$livetime); 
 document.cookie = name+"="+value+";expires="+date.toGMTString();
}
// 设置cookie
$_cookie("param","javascript设置cookie");
</script>