在`laravel`中我们经常需要将二维数组转为一维数组，
如果直接写`foreach`会比较笨重
有没有简单的方法
比如，我们想将以下二维数组
```
$arr = array(
[ 'name' => "username1", "email" => "username1@qq.com"],
[ 'name' => "username2", "email" => "username2@qq.com"],
[ 'name' => "username3", "email" => "username3@qq.com"],
);
```
转化成
```
$data = array( "username1" => "username1@qq.com", "username2" => "username2@qq.com", "username3" =>"username3@qq.com" );
```
方法一:
`$data = array_column($arr,'email','name');`
方法二:
`$data = collect($arr)->pluck("email","name");`
方法三:
```
$data = collect($arr)->reduce(function($lookup,$item){
$lookup[$item["name"]] = $item["email"]; return $lookup;
},[]);
```
