如何在php中设置cookie，在js中获取

<?php

            setcookie("key","value",0,"/");

?>

<script>        
   function getCookie(key){
if (document.cookie.length > 0){
    c_start = document.cookie.indexOf(c_name + "=");
    if (c_start != -1){
        c_start = c_start + c_name.length + 1;
        c_end = document.cookie.indexOf(";", c_start);
        if (c_end == -1){
            c_end = document.cookie.length;
        }
        return unescape(document.cookie.substring(c_start, c_end));
    }
}return "";

}
alert(getCookie(key));
//打印cookie的值
</script>