当参数是整数但不是字符串时，javascript onclick函数有效吗？

Question

echo '<a onclick="load_tags('.$list['id'].')"></a>'

when list[id] is a number, it works. but when list[id] is a word, it does not work. why?

below is some background on the function and what i am doing. although it is not necessary for the purposes of answering this question.

script

function load_tags(id){
        $.post('../php/tags/get_tags.php',{id:id},function(data){
            $('#tags_selected').text(data);
        });
    }

get_tags.php

$tag_id=$_POST['id'];
    echo $tag_id;
    $users_with_this_tag=show_all_users_with_this_tag($tag_id);
    if(count($users_with_this_tag)!=0){
            foreach($users_with_this_tag as $key => $list){
                echo $list['user_id'];
            }
    }else{
        echo'Nobody with this tag';
    }

Answer 1

Just surround load_tags argument with escaped single quotes:

echo '<a onclick="load_tags(\''.$list['id'].'\')"></a>';