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

$array=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')

);

foreach($array as $key=>$value){

	$newarray[$key]=$value['mobile'];

}

return join(",",$newarray);

$array=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')

);

foreach($array as $key=>$value){

	$mobile.=$dot.$value['mobile'];

	$dot=",";

}

return $mobile;