关于js的cookie问题

我在js文件里面获取cookie的值，发现下面的情况：

这是我alert（document.cookie）的值：SESSID=68746e4edec9ea6b3460f46e0f43a535; deal_city=2; cnzz_a2262545=21; sin2262545=; rtime=0; ltime=1311071576665; cnzz_eid=98221199-1311068091-; Hm_lpvt_68c60e793dd351a567b8ef274af22abf=1311070394338; Hm_lvt_68c60e793dd351a567b8ef274af22abf=1311069789016


然后我在PHP页面打印Cookie的值，
Array ( [SESSID] => 68746e4edec9ea6b3460f46e0f43a535 [deal_city] => 2 [cnzz_a2262545] => 21 [sin2262545] => [rtime] => 0 [ltime] => 1311071576665 [cnzz_eid] => 98221199-1311068091- [Hm_lpvt_68c60e793dd351a567b8ef274af22abf] => 1311070394338 [Hm_lvt_68c60e793dd351a567b8ef274af22abf] => 1311069789016 [frontend] => cd59c6557e71e28ecdc70f07f0d9d18f [channelid] => 51 [u_id] => 21 [username] => [email protected] ) 

结果是JS就是找不到我要的channelid这个参数值。请问是什么原因？

document.cookie 返回的是当前应用的所有cookie 
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