二组数据分割成字符串以“，”隔开,该如何解决

二组数据分割成字符串以“，”隔开
Array
(
    [0] => Array
        (
            [mobile] => 13814002394
        )

    [1] => Array
        (
            [mobile] => 13814002395
        )

    [2] => Array
        (
            [mobile] => 13814002396
        )

    [3] => Array
        (
            [mobile] => 13814002397
        )

    [4] => Array
        (
            [mobile] => 13814002398
        )

    [5] => Array
        (
            [mobile] => 13814002399
        )

    [6] => Array
        (
            [mobile] => 13814002400
        )
）

这是得出的二组数组，我想分割成字符串 $mobile=13814002399,13814002400,13814002398;

这样只的形式

<br />
$array=array(<br />
	'0'=>array('mobile'=>'13814002394'),<br />
	'1'=>array('mobile'=>'13814002395'),       <br />
	'2'=>array('mobile'=>'13814002396'),<br />
	'3'=>array('mobile'=>'13814002397'),<br />
	'4'=>array('mobile'=>'13814002398'),<br />
	'5'=>array('mobile'=>'13814002399'),<br />
	'6'=>array('mobile'=>'13814002400')<br />
);<br />
foreach($array as $key=>$value){<br />
	$newarray[$key]=$value['mobile'];<br />
}<br />
return join(",",$newarray);<br />

<br />
<br />
$array=array(<br />
	'0'=>array('mobile'=>'13814002394'),<br />
	'1'=>array('mobile'=>'13814002395'),       <br />
	'2'=>array('mobile'=>'13814002396'),<br />
	'3'=>array('mobile'=>'13814002397'),<br />
	'4'=>array('mobile'=>'13814002398'),<br />
	'5'=>array('mobile'=>'13814002399'),<br />
	'6'=>array('mobile'=>'13814002400')<br />
);<br />
foreach($array as $key=>$value){<br />
	$mobile.=$dot.$value['mobile'];<br />
	$dot=",";<br />
}<br />
return $mobile;<br />
<br />