字符串转化作数字？

字符串转化为数字？？？
今天遇到个比较奇怪的现象，很可能是我储备还不够吧，包含引号的数字的字符串转化为数字时出现了问题

"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"

上面的为一段数据，接下来操作

$arr = '"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"';
$arr = explode(',',$arr);
print_r($arr);

打印

Array
(
    [0] => "1000"
    [1] => "902865066306"
    [2] => "02865066306"
    [3] => "SIP Phone"
    [4] => "IP Trunk"
    [5] => ""
    [6] => "trunk20"
    [7] => "ON2OFF"
    [8] => "1333230069"
    [9] => "1333230072"
    [10] => "1333230134"
    [11] => "65"
    [12] => "62"
    [13] => "Connected"
)

我想把数组里的第九个拿出来来和其他的数据比较，平常把引号包围的字符串转为数字时就是在后面加个0就ok了，可是，今天不一样了

echo $arr[8] + 0; //

结果为0

我就纳闷了，怎么会为0呢，$arr[8]明明有值啊，于是我又测试了下

$num = "1333230069";
echo $num+0;//1333230069

弄了好久没明白怎么回事，后来就用了两个办法解决了，一个是用正则把数字提出来，另一个是一开始就把字符串里的双引号全都替换为空。

可是疑惑还没有解决，啰嗦到现在，就是想问问大大们，为什么上面的做法会出现0的结果，而不是想要的数字。

------最佳解决方案--------------------
var_dump($arr[8]); //string(12) ""1333230069""
var_dump($num); //string(10) "1333230069"

这样看就清楚了，将 $arr[8] 的首尾双引号去掉后再运算就对了。
------其他解决方案--------------------
没必要那么麻烦吧？

$arr = '"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"';
$t = json_decode("[$arr]");
print_r($t);

Array
(
[0] => 1000
[1] => 902865066306
[2] => 02865066306
[3] => SIP Phone
[4] => IP Trunk
[5] =>
[6] => trunk20
[7] => ON2OFF
[8] => 1333230069
[9] => 1333230072
[10] => 1333230134
[11] => 65
[12] => 62
[13] => Connected
)

也可以
$t = array_map( function($s) { return trim($s,'"'); }, explode(',', $arr)); // >= php 5.3
也可以
$t = array_map( create_function('$s', 'return trim($s,\'"\');'), explode(',', $arr)); // >= php 4

直接就处理成可用的数组
------其他解决方案--------------------
对于你的疑问
不错
$num = "1333230069";
echo $num+0;//1333230069

但是 $arr[8] 是什么呢？