如何从数组中获取键值？

这是数组:

$campaigns = 
Array (
[252] =>Array ( 
        [campaign_type_id] => 9 
        [company] => Array ( 
                    [company_name] => facebook 
                    [company_type] => 2 
                   )
        [campaign] => Array(
                    [pitch_id] => 27 
                    [pitch_campaign_title] => facebook mandate 
                        [pitch_campaign_description] => desc face 
                    [pitch_campaign_image] => db.png 
                   )
        [title] => Accelarator 
        [selection] => Array ( 
                    [0] => Array(
                             [ca_mandate_id] => 96 
                            [ca_id] => 252 
                            [ca_company_id] => 1 
                            [ca_updated] => 2015-12-31 12:37:50
                            )
                    ) 
        [campaign_created_by] => 3 
        [userinfo] => Array ( 
                    [0] => Array ( 
                            [user_id] => 3 
                            [user_first_name] => CoLabs 
                            [user_last_name] => Accelerator 
                            [user_img] => index2.jpg 
                            [user_designation_name] => Investor
                             [user_company_id] => 123
                              )
                     )
         )
   )

我怎样才能得到'252'的值？它是一个动态的价值.我希望得到任何存储的值代替252.

请帮忙？

提前致谢.

使用array_keys函数:http://php.net/array_keys

array_keys - 返回数组的所有键或键的子集

描述 array array_keys(array $ array [,mixed $ search_value = null [,bool $ strict = false]])

对于你的代码:

$keys = array_keys($campaigns);